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 $129.53   13.717%   $147.2976   $147.30   $147.30   $147.30  
  Purchase #2 $84.62   13.645%   $96.1664   $96.17   $96.15   $96.20  
  Purchase #3 $202.47   5.689%   $213.9885   $213.99   $214.00   $214.00  
  Purchase #4 $76.57   12.564%   $86.1903   $86.19   $86.20   $86.20  
  Purchase #5 $172.39   13.754%   $196.1005   $196.10   $196.10   $196.10  
  Purchase #6 $110.27   11.648%   $123.1142   $123.11   $123.10   $123.10  
  Purchase #7 $137.54   7.472%   $147.817   $147.82   $147.80   $147.80  
  7 purchase totals = $913.39       $1,010.6745   $1,010.68   $1,010.65   $1,010.70