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 $208.90   11.155%   $232.2028   $232.20   $232.20   $232.20  
  Purchase #2 $6.93   9.639%   $7.598   $7.60   $7.60   $7.60  
  Purchase #3 $145.98   10.771%   $161.7035   $161.70   $161.70   $161.70  
  Purchase #4 $211.41   12.298%   $237.4092   $237.41   $237.40   $237.40  
  Purchase #5 $136.75   13.539%   $155.2646   $155.26   $155.25   $155.30  
  Purchase #6 $191.51   9.434%   $209.5771   $209.58   $209.60   $209.60  
  Purchase #7 $44.47   13.734%   $50.5775   $50.58   $50.60   $50.60  
  7 purchase totals = $945.95       $1,054.3327   $1,054.33   $1,054.35   $1,054.40