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 $147.55   10.190%   $162.5853   $162.59   $162.60   $162.60  
  Purchase #2 $243.31   8.724%   $264.5364   $264.54   $264.55   $264.50  
  Purchase #3 $66.82   13.248%   $75.6723   $75.67   $75.65   $75.70  
  Purchase #4 $168.29   3.256%   $173.7695   $173.77   $173.75   $173.80  
  Purchase #5 $216.37   11.588%   $241.443   $241.44   $241.45   $241.40  
  Purchase #6 $59.33   9.611%   $65.0322   $65.03   $65.05   $65.00  
  Purchase #7 $151.93   11.703%   $169.7104   $169.71   $169.70   $169.70  
  7 purchase totals = $1,053.60       $1,152.7491   $1,152.75   $1,152.75   $1,152.70