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 $85.67   9.713%   $93.9911   $93.99   $94.00   $94.00  
  Purchase #2 $199.45   5.461%   $210.342   $210.34   $210.35   $210.30  
  Purchase #3 $68.83   4.133%   $71.6747   $71.67   $71.65   $71.70  
  Purchase #4 $178.55   13.315%   $202.3239   $202.32   $202.30   $202.30  
  Purchase #5 $215.35   7.374%   $231.2299   $231.23   $231.25   $231.20  
  Purchase #6 $57.33   10.506%   $63.3531   $63.35   $63.35   $63.40  
  Purchase #7 $204.29   10.820%   $226.3942   $226.39   $226.40   $226.40  
  7 purchase totals = $1,009.47       $1,099.3089   $1,099.29   $1,099.30   $1,099.30