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 $61.52   3.801%   $63.8584   $63.86   $63.85   $63.90  
  Purchase #2 $206.36   6.337%   $219.437   $219.44   $219.45   $219.40  
  Purchase #3 $42.85   11.514%   $47.7837   $47.78   $47.80   $47.80  
  Purchase #4 $46.55   10.155%   $51.2772   $51.28   $51.30   $51.30  
  Purchase #5 $239.56   8.814%   $260.6748   $260.67   $260.65   $260.70  
  Purchase #6 $115.77   11.496%   $129.0789   $129.08   $129.10   $129.10  
  Purchase #7 $209.49   7.693%   $225.6061   $225.61   $225.60   $225.60  
  7 purchase totals = $922.10       $997.7161   $997.72   $997.75   $997.80