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 $184.68   5.504%   $194.8448   $194.84   $194.85   $194.80  
  Purchase #2 $224.85   9.151%   $245.426   $245.43   $245.45   $245.40  
  Purchase #3 $53.64   4.465%   $56.035   $56.04   $56.05   $56.00  
  Purchase #4 $162.64   6.664%   $173.4783   $173.48   $173.50   $173.50  
  Purchase #5 $180.59   10.758%   $200.0179   $200.02   $200.00   $200.00  
  Purchase #6 $201.49   13.648%   $228.9894   $228.99   $229.00   $229.00  
  Purchase #7 $191.32   7.529%   $205.7245   $205.72   $205.70   $205.70  
  7 purchase totals = $1,199.21       $1,304.5159   $1,304.52   $1,304.55   $1,304.40