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 $87.35   8.754%   $94.9966   $95.00   $95.00   $95.00  
  Purchase #2 $120.41   6.188%   $127.861   $127.86   $127.85   $127.90  
  Purchase #3 $114.87   12.859%   $129.6411   $129.64   $129.65   $129.60  
  Purchase #4 $104.46   5.603%   $110.3129   $110.31   $110.30   $110.30  
  Purchase #5 $170.46   12.852%   $192.3675   $192.37   $192.35   $192.40  
  Purchase #6 $70.87   11.493%   $79.0151   $79.02   $79.00   $79.00  
  Purchase #7 $63.53   6.472%   $67.6417   $67.64   $67.65   $67.60  
  7 purchase totals = $731.95       $801.8359   $801.84   $801.80   $801.80