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 $119.86   5.253%   $126.1562   $126.16   $126.15   $126.20  
  Purchase #2 $61.29   5.393%   $64.5954   $64.60   $64.60   $64.60  
  Purchase #3 $168.67   5.529%   $177.9958   $178.00   $178.00   $178.00  
  Purchase #4 $85.58   9.356%   $93.5869   $93.59   $93.60   $93.60  
  Purchase #5 $165.81   4.538%   $173.3345   $173.33   $173.35   $173.30  
  Purchase #6 $219.63   9.461%   $240.4092   $240.41   $240.40   $240.40  
  Purchase #7 $139.77   7.641%   $150.4498   $150.45   $150.45   $150.40  
  7 purchase totals = $960.61       $1,026.5278   $1,026.54   $1,026.55   $1,026.50