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 $216.59   11.581%   $241.6733   $241.67   $241.65   $241.70  
  Purchase #2 $200.39   9.571%   $219.5693   $219.57   $219.55   $219.60  
  Purchase #3 $5.52   8.547%   $5.9918   $5.99   $6.00   $6.00  
  Purchase #4 $114.95   4.167%   $119.74   $119.74   $119.75   $119.70  
  Purchase #5 $209.73   5.167%   $220.5667   $220.57   $220.55   $220.60  
  Purchase #6 $230.86   5.824%   $244.3053   $244.31   $244.30   $244.30  
  Purchase #7 $39.76   8.636%   $43.1937   $43.19   $43.20   $43.20  
  7 purchase totals = $1,017.80       $1,095.0401   $1,095.04   $1,095.00   $1,095.10