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 $62.96   9.585%   $68.9947   $68.99   $69.00   $69.00  
  Purchase #2 $198.77   10.202%   $219.0485   $219.05   $219.05   $219.00  
  Purchase #3 $242.97   6.236%   $258.1216   $258.12   $258.10   $258.10  
  Purchase #4 $223.63   10.406%   $246.9009   $246.90   $246.90   $246.90  
  Purchase #5 $81.77   12.816%   $92.2496   $92.25   $92.25   $92.20  
  Purchase #6 $20.55   11.177%   $22.8469   $22.85   $22.85   $22.80  
  Purchase #7 $143.97   5.592%   $152.0208   $152.02   $152.00   $152.00  
  7 purchase totals = $974.62       $1,060.1830   $1,060.18   $1,060.15   $1,060.00