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 $43.48   3.823%   $45.1422   $45.14   $45.15   $45.10  
  Purchase #2 $165.38   6.212%   $175.6534   $175.65   $175.65   $175.70  
  Purchase #3 $224.69   4.194%   $234.1135   $234.11   $234.10   $234.10  
  Purchase #4 $191.75   4.702%   $200.7661   $200.77   $200.75   $200.80  
  Purchase #5 $147.42   9.224%   $161.018   $161.02   $161.00   $161.00  
  Purchase #6 $230.78   6.803%   $246.48   $246.48   $246.50   $246.50  
  Purchase #7 $56.71   8.851%   $61.7294   $61.73   $61.75   $61.70  
  7 purchase totals = $1,060.21       $1,124.9026   $1,124.90   $1,124.90   $1,124.90