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 $93.57   13.711%   $106.3994   $106.40   $106.40   $106.40  
  Purchase #2 $188.78   11.472%   $210.4368   $210.44   $210.45   $210.40  
  Purchase #3 $36.55   13.835%   $41.6067   $41.61   $41.60   $41.60  
  Purchase #4 $95.98   10.453%   $106.0128   $106.01   $106.00   $106.00  
  Purchase #5 $83.95   9.155%   $91.6356   $91.64   $91.65   $91.60  
  Purchase #6 $167.47   11.351%   $186.4795   $186.48   $186.50   $186.50  
  Purchase #7 $140.40   6.831%   $149.9907   $149.99   $150.00   $150.00  
  7 purchase totals = $806.70       $892.5615   $892.57   $892.60   $892.50