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 $60.64   13.861%   $69.0453   $69.05   $69.05   $69.00  
  Purchase #2 $181.58   3.658%   $188.2222   $188.22   $188.20   $188.20  
  Purchase #3 $161.82   11.286%   $180.083   $180.08   $180.10   $180.10  
  Purchase #4 $59.92   3.693%   $62.1328   $62.13   $62.15   $62.10  
  Purchase #5 $240.43   4.636%   $251.5763   $251.58   $251.60   $251.60  
  Purchase #6 $12.80   9.653%   $14.0356   $14.04   $14.05   $14.00  
  Purchase #7 $184.57   3.112%   $190.3138   $190.31   $190.30   $190.30  
  7 purchase totals = $901.76       $955.4090   $955.41   $955.45   $955.30