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 $196.85   5.276%   $207.2358   $207.24   $207.25   $207.20  
  Purchase #2 $173.75   3.868%   $180.4707   $180.47   $180.45   $180.50  
  Purchase #3 $19.49   5.651%   $20.5914   $20.59   $20.60   $20.60  
  Purchase #4 $85.52   7.709%   $92.1127   $92.11   $92.10   $92.10  
  Purchase #5 $245.45   9.124%   $267.8449   $267.84   $267.85   $267.80  
  Purchase #6 $219.69   3.399%   $227.1573   $227.16   $227.15   $227.20  
  Purchase #7 $120.28   4.229%   $125.3666   $125.37   $125.35   $125.40  
  7 purchase totals = $1,061.03       $1,120.7794   $1,120.78   $1,120.75   $1,120.80