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 $77.93   11.151%   $86.62   $86.62   $86.60   $86.60  
  Purchase #2 $227.82   4.375%   $237.7871   $237.79   $237.80   $237.80  
  Purchase #3 $55.85   4.790%   $58.5252   $58.53   $58.55   $58.50  
  Purchase #4 $27.40   4.573%   $28.653   $28.65   $28.65   $28.70  
  Purchase #5 $232.86   3.237%   $240.3977   $240.40   $240.40   $240.40  
  Purchase #6 $161.72   3.711%   $167.7214   $167.72   $167.70   $167.70  
  Purchase #7 $192.97   6.735%   $205.9665   $205.97   $205.95   $206.00  
  7 purchase totals = $976.55       $1,025.6709   $1,025.68   $1,025.65   $1,025.70