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 $114.79   9.621%   $125.8339   $125.83   $125.85   $125.80  
  Purchase #2 $160.84   10.257%   $177.3374   $177.34   $177.35   $177.30  
  Purchase #3 $204.68   3.475%   $211.7926   $211.79   $211.80   $211.80  
  Purchase #4 $68.67   5.682%   $72.5718   $72.57   $72.55   $72.60  
  Purchase #5 $220.64   4.150%   $229.7966   $229.80   $229.80   $229.80  
  Purchase #6 $80.42   3.332%   $83.0996   $83.10   $83.10   $83.10  
  Purchase #7 $145.40   5.765%   $153.7823   $153.78   $153.80   $153.80  
  7 purchase totals = $995.44       $1,054.2142   $1,054.21   $1,054.25   $1,054.20