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 $151.60   11.871%   $169.5964   $169.60   $169.60   $169.60  
  Purchase #2 $84.90   10.739%   $94.0174   $94.02   $94.00   $94.00  
  Purchase #3 $216.94   5.392%   $228.6374   $228.64   $228.65   $228.60  
  Purchase #4 $197.78   6.650%   $210.9324   $210.93   $210.95   $210.90  
  Purchase #5 $177.51   6.767%   $189.5221   $189.52   $189.50   $189.50  
  Purchase #6 $79.87   10.313%   $88.107   $88.11   $88.10   $88.10  
  Purchase #7 $167.58   3.650%   $173.6967   $173.70   $173.70   $173.70  
  7 purchase totals = $1,076.18       $1,154.5094   $1,154.52   $1,154.50   $1,154.40