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 $128.49   13.644%   $146.0212   $146.02   $146.00   $146.00  
  Purchase #2 $203.79   13.696%   $231.7011   $231.70   $231.70   $231.70  
  Purchase #3 $115.50   9.415%   $126.3743   $126.37   $126.35   $126.40  
  Purchase #4 $52.28   7.770%   $56.3422   $56.34   $56.35   $56.30  
  Purchase #5 $89.69   3.469%   $92.8013   $92.80   $92.80   $92.80  
  Purchase #6 $208.32   8.764%   $226.5772   $226.58   $226.60   $226.60  
  Purchase #7 $216.94   11.764%   $242.4608   $242.46   $242.45   $242.50  
  7 purchase totals = $1,015.01       $1,122.2781   $1,122.27   $1,122.25   $1,122.30