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 $97.52   8.467%   $105.777   $105.78   $105.80   $105.80  
  Purchase #2 $170.27   13.322%   $192.9534   $192.95   $192.95   $193.00  
  Purchase #3 $53.97   13.364%   $61.1826   $61.18   $61.20   $61.20  
  Purchase #4 $111.98   13.522%   $127.1219   $127.12   $127.10   $127.10  
  Purchase #5 $206.66   10.804%   $228.9875   $228.99   $229.00   $229.00  
  Purchase #6 $183.50   8.742%   $199.5416   $199.54   $199.55   $199.50  
  Purchase #7 $215.99   13.814%   $245.8269   $245.83   $245.85   $245.80  
  7 purchase totals = $1,039.89       $1,161.3909   $1,161.39   $1,161.45   $1,161.40