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 $64.84   6.628%   $69.1376   $69.14   $69.15   $69.10  
  Purchase #2 $219.60   13.852%   $250.019   $250.02   $250.00   $250.00  
  Purchase #3 $135.98   12.676%   $153.2168   $153.22   $153.20   $153.20  
  Purchase #4 $76.68   12.635%   $86.3685   $86.37   $86.35   $86.40  
  Purchase #5 $188.33   9.194%   $205.6451   $205.65   $205.65   $205.60  
  Purchase #6 $111.29   12.361%   $125.0466   $125.05   $125.05   $125.00  
  Purchase #7 $150.70   13.575%   $171.1575   $171.16   $171.15   $171.20  
  7 purchase totals = $947.42       $1,060.5911   $1,060.61   $1,060.55   $1,060.50