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 $81.75   7.455%   $87.8445   $87.84   $87.85   $87.80  
  Purchase #2 $87.56   9.586%   $95.9535   $95.95   $95.95   $96.00  
  Purchase #3 $175.73   3.568%   $182   $182.00   $182.00   $182.00  
  Purchase #4 $186.32   6.818%   $199.0233   $199.02   $199.00   $199.00  
  Purchase #5 $236.82   6.757%   $252.8219   $252.82   $252.80   $252.80  
  Purchase #6 $192.51   10.114%   $211.9805   $211.98   $212.00   $212.00  
  Purchase #7 $53.57   10.138%   $59.0009   $59.00   $59.00   $59.00  
  7 purchase totals = $1,014.26       $1,088.6246   $1,088.61   $1,088.60   $1,088.60