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 $86.44   11.702%   $96.5552   $96.56   $96.55   $96.60  
  Purchase #2 $72.39   3.134%   $74.6587   $74.66   $74.65   $74.70  
  Purchase #3 $242.79   4.589%   $253.9316   $253.93   $253.95   $253.90  
  Purchase #4 $216.95   13.252%   $245.7002   $245.70   $245.70   $245.70  
  Purchase #5 $212.48   3.437%   $219.7829   $219.78   $219.80   $219.80  
  Purchase #6 $168.26   3.236%   $173.7049   $173.70   $173.70   $173.70  
  Purchase #7 $60.57   3.653%   $62.7826   $62.78   $62.80   $62.80  
  7 purchase totals = $1,059.88       $1,127.1161   $1,127.11   $1,127.15   $1,127.20