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 $84.65   12.271%   $95.0374   $95.04   $95.05   $95.00  
  Purchase #2 $186.35   13.359%   $211.2445   $211.24   $211.25   $211.20  
  Purchase #3 $231.69   6.409%   $246.539   $246.54   $246.55   $246.50  
  Purchase #4 $243.89   13.783%   $277.5054   $277.51   $277.50   $277.50  
  Purchase #5 $67.36   10.210%   $74.2375   $74.24   $74.25   $74.20  
  Purchase #6 $138.33   10.748%   $153.1977   $153.20   $153.20   $153.20  
  Purchase #7 $108.52   11.765%   $121.2874   $121.29   $121.30   $121.30  
  7 purchase totals = $1,060.79       $1,179.0489   $1,179.06   $1,179.10   $1,178.90