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 $184.37   7.166%   $197.582   $197.58   $197.60   $197.60  
  Purchase #2 $194.86   4.709%   $204.036   $204.04   $204.05   $204.00  
  Purchase #3 $64.52   4.653%   $67.5221   $67.52   $67.50   $67.50  
  Purchase #4 $46.85   10.258%   $51.6559   $51.66   $51.65   $51.70  
  Purchase #5 $8.41   8.748%   $9.1457   $9.15   $9.15   $9.10  
  Purchase #6 $215.51   11.753%   $240.8389   $240.84   $240.85   $240.80  
  Purchase #7 $243.73   6.746%   $260.172   $260.17   $260.15   $260.20  
  7 purchase totals = $958.25       $1,030.9526   $1,030.96   $1,030.95   $1,030.90