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 $67.37   12.837%   $76.0183   $76.02   $76.00   $76.00  
  Purchase #2 $200.67   5.468%   $211.6426   $211.64   $211.65   $211.60  
  Purchase #3 $234.46   3.755%   $243.264   $243.26   $243.25   $243.30  
  Purchase #4 $44.64   4.366%   $46.589   $46.59   $46.60   $46.60  
  Purchase #5 $58.30   3.407%   $60.2863   $60.29   $60.30   $60.30  
  Purchase #6 $216.81   3.418%   $224.2206   $224.22   $224.20   $224.20  
  Purchase #7 $212.28   8.723%   $230.7972   $230.80   $230.80   $230.80  
  7 purchase totals = $1,034.53       $1,092.8180   $1,092.82   $1,092.80   $1,092.80