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 $63.33   13.295%   $71.7497   $71.75   $71.75   $71.70  
  Purchase #2 $190.48   3.185%   $196.5468   $196.55   $196.55   $196.50  
  Purchase #3 $226.58   12.151%   $254.1117   $254.11   $254.10   $254.10  
  Purchase #4 $45.42   4.842%   $47.6192   $47.62   $47.60   $47.60  
  Purchase #5 $121.45   13.613%   $137.983   $137.98   $138.00   $138.00  
  Purchase #6 $186.52   13.641%   $211.9632   $211.96   $211.95   $212.00  
  Purchase #7 $189.68   9.472%   $207.6465   $207.65   $207.65   $207.60  
  7 purchase totals = $1,023.46       $1,127.6201   $1,127.62   $1,127.60   $1,127.50