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 $212.56   4.742%   $222.6396   $222.64   $222.65   $222.60  
  Purchase #2 $75.99   8.829%   $82.6992   $82.70   $82.70   $82.70  
  Purchase #3 $141.66   8.449%   $153.6289   $153.63   $153.65   $153.60  
  Purchase #4 $178.87   8.113%   $193.3817   $193.38   $193.40   $193.40  
  Purchase #5 $80.84   5.541%   $85.3193   $85.32   $85.30   $85.30  
  Purchase #6 $76.51   11.401%   $85.2329   $85.23   $85.25   $85.20  
  Purchase #7 $201.58   8.679%   $219.0751   $219.08   $219.10   $219.10  
  7 purchase totals = $968.01       $1,041.9767   $1,041.98   $1,042.05   $1,041.90