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 $88.95   5.335%   $93.6955   $93.70   $93.70   $93.70  
  Purchase #2 $166.67   7.614%   $179.3603   $179.36   $179.35   $179.40  
  Purchase #3 $187.64   8.106%   $202.8501   $202.85   $202.85   $202.90  
  Purchase #4 $46.87   4.273%   $48.8728   $48.87   $48.85   $48.90  
  Purchase #5 $154.28   3.106%   $159.0719   $159.07   $159.05   $159.10  
  Purchase #6 $191.48   6.534%   $203.9913   $203.99   $204.00   $204.00  
  Purchase #7 $220.29   4.799%   $230.8617   $230.86   $230.85   $230.90  
  7 purchase totals = $1,056.18       $1,118.7036   $1,118.70   $1,118.65   $1,118.90