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 $187.80   9.619%   $205.8645   $205.86   $205.85   $205.90  
  Purchase #2 $228.65   8.314%   $247.66   $247.66   $247.65   $247.70  
  Purchase #3 $61.34   9.754%   $67.3231   $67.32   $67.30   $67.30  
  Purchase #4 $226.42   4.662%   $236.9757   $236.98   $237.00   $237.00  
  Purchase #5 $115.43   9.184%   $126.0311   $126.03   $126.05   $126.00  
  Purchase #6 $72.35   4.398%   $75.532   $75.53   $75.55   $75.50  
  Purchase #7 $144.91   7.325%   $155.5247   $155.52   $155.50   $155.50  
  7 purchase totals = $1,036.90       $1,114.9111   $1,114.90   $1,114.90   $1,114.90