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 $88.76   7.253%   $95.1978   $95.20   $95.20   $95.20  
  Purchase #2 $148.77   13.137%   $168.3139   $168.31   $168.30   $168.30  
  Purchase #3 $180.31   6.670%   $192.3367   $192.34   $192.35   $192.30  
  Purchase #4 $17.58   9.335%   $19.2211   $19.22   $19.20   $19.20  
  Purchase #5 $155.50   8.510%   $168.7331   $168.73   $168.75   $168.70  
  Purchase #6 $210.91   12.280%   $236.8097   $236.81   $236.80   $236.80  
  Purchase #7 $160.26   12.350%   $180.0521   $180.05   $180.05   $180.10  
  7 purchase totals = $962.09       $1,060.6644   $1,060.66   $1,060.65   $1,060.60