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 $104.40   9.802%   $114.6333   $114.63   $114.65   $114.60  
  Purchase #2 $150.59   13.526%   $170.9588   $170.96   $170.95   $171.00  
  Purchase #3 $212.26   13.858%   $241.675   $241.68   $241.70   $241.70  
  Purchase #4 $110.32   9.522%   $120.8247   $120.82   $120.80   $120.80  
  Purchase #5 $156.52   10.284%   $172.6165   $172.62   $172.60   $172.60  
  Purchase #6 $77.80   13.543%   $88.3365   $88.34   $88.35   $88.30  
  Purchase #7 $221.83   13.731%   $252.2895   $252.29   $252.30   $252.30  
  7 purchase totals = $1,033.72       $1,161.3343   $1,161.34   $1,161.35   $1,161.30