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 $67.35   11.333%   $74.9828   $74.98   $75.00   $75.00  
  Purchase #2 $248.47   8.370%   $269.2669   $269.27   $269.25   $269.30  
  Purchase #3 $156.95   5.205%   $165.1192   $165.12   $165.10   $165.10  
  Purchase #4 $211.35   4.604%   $221.0806   $221.08   $221.10   $221.10  
  Purchase #5 $193.76   3.494%   $200.53   $200.53   $200.55   $200.50  
  Purchase #6 $182.72   6.467%   $194.5365   $194.54   $194.55   $194.50  
  Purchase #7 $76.55   11.294%   $85.1956   $85.20   $85.20   $85.20  
  7 purchase totals = $1,137.15       $1,210.7116   $1,210.72   $1,210.75   $1,210.70