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 $174.52   13.264%   $197.6683   $197.67   $197.65   $197.70  
  Purchase #2 $214.41   6.413%   $228.1601   $228.16   $228.15   $228.20  
  Purchase #3 $215.90   11.218%   $240.1197   $240.12   $240.10   $240.10  
  Purchase #4 $96.79   11.754%   $108.1667   $108.17   $108.15   $108.20  
  Purchase #5 $61.72   5.796%   $65.2973   $65.30   $65.30   $65.30  
  Purchase #6 $215.55   10.395%   $237.9564   $237.96   $237.95   $238.00  
  Purchase #7 $75.84   11.718%   $84.7269   $84.73   $84.75   $84.70  
  7 purchase totals = $1,054.73       $1,162.0954   $1,162.11   $1,162.05   $1,162.20