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 $92.46   13.694%   $105.1215   $105.12   $105.10   $105.10  
  Purchase #2 $26.25   11.714%   $29.3249   $29.32   $29.30   $29.30  
  Purchase #3 $65.63   3.343%   $67.824   $67.82   $67.80   $67.80  
  Purchase #4 $89.39   5.158%   $94.0007   $94.00   $94.00   $94.00  
  Purchase #5 $218.28   12.854%   $246.3377   $246.34   $246.35   $246.30  
  Purchase #6 $167.62   5.782%   $177.3118   $177.31   $177.30   $177.30  
  Purchase #7 $156.92   3.118%   $161.8128   $161.81   $161.80   $161.80  
  7 purchase totals = $816.55       $881.7334   $881.72   $881.65   $881.60