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 $81.65   3.723%   $84.6898   $84.69   $84.70   $84.70  
  Purchase #2 $194.48   6.339%   $206.8081   $206.81   $206.80   $206.80  
  Purchase #3 $67.61   11.751%   $75.5549   $75.55   $75.55   $75.60  
  Purchase #4 $116.77   3.596%   $120.969   $120.97   $120.95   $121.00  
  Purchase #5 $203.49   8.457%   $220.6991   $220.70   $220.70   $220.70  
  Purchase #6 $186.31   6.530%   $198.476   $198.48   $198.50   $198.50  
  Purchase #7 $103.49   3.694%   $107.3129   $107.31   $107.30   $107.30  
  7 purchase totals = $953.80       $1,014.5098   $1,014.51   $1,014.50   $1,014.60