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 $95.86   10.683%   $106.1007   $106.10   $106.10   $106.10  
  Purchase #2 $87.69   11.621%   $97.8805   $97.88   $97.90   $97.90  
  Purchase #3 $185.98   8.205%   $201.2397   $201.24   $201.25   $201.20  
  Purchase #4 $210.40   8.642%   $228.5828   $228.58   $228.60   $228.60  
  Purchase #5 $169.60   11.619%   $189.3058   $189.31   $189.30   $189.30  
  Purchase #6 $17.71   9.404%   $19.3754   $19.38   $19.40   $19.40  
  Purchase #7 $199.35   9.871%   $219.0278   $219.03   $219.05   $219.00  
  7 purchase totals = $966.59       $1,061.5127   $1,061.52   $1,061.60   $1,061.50