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 $58.64   3.767%   $60.849   $60.85   $60.85   $60.80  
  Purchase #2 $225.45   10.242%   $248.5406   $248.54   $248.55   $248.50  
  Purchase #3 $38.60   8.389%   $41.8382   $41.84   $41.85   $41.80  
  Purchase #4 $212.93   6.807%   $227.4241   $227.42   $227.40   $227.40  
  Purchase #5 $45.31   9.391%   $49.5651   $49.57   $49.55   $49.60  
  Purchase #6 $190.85   6.546%   $203.343   $203.34   $203.35   $203.30  
  Purchase #7 $198.52   10.667%   $219.6961   $219.70   $219.70   $219.70  
  7 purchase totals = $970.30       $1,051.2561   $1,051.26   $1,051.25   $1,051.10