Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $191.56   7.751%   $206.4078   $206.41   $206.40   $206.40  
  Purchase #2 $108.87   9.293%   $118.9873   $118.99   $119.00   $119.00  
  Purchase #3 $109.40   13.623%   $124.3036   $124.30   $124.30   $124.30  
  Purchase #4 $244.47   10.262%   $269.5575   $269.56   $269.55   $269.60  
  Purchase #5 $108.64   8.804%   $118.2047   $118.20   $118.20   $118.20  
  Purchase #6 $108.99   6.106%   $115.6449   $115.64   $115.65   $115.60  
  Purchase #7 $150.51   3.363%   $155.5717   $155.57   $155.55   $155.60  
  7 purchase totals = $1,022.44       $1,108.6775   $1,108.67   $1,108.65   $1,108.70