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 $197.60   4.740%   $206.9662   $206.97   $206.95   $207.00  
  Purchase #2 $235.29   4.317%   $245.4475   $245.45   $245.45   $245.40  
  Purchase #3 $35.96   13.495%   $40.8128   $40.81   $40.80   $40.80  
  Purchase #4 $188.35   13.229%   $213.2668   $213.27   $213.25   $213.30  
  Purchase #5 $243.56   13.123%   $275.5224   $275.52   $275.50   $275.50  
  Purchase #6 $168.33   6.597%   $179.4347   $179.43   $179.45   $179.40  
  Purchase #7 $60.97   4.596%   $63.7722   $63.77   $63.75   $63.80  
  7 purchase totals = $1,130.06       $1,225.2226   $1,225.22   $1,225.15   $1,225.20