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 $169.31   4.346%   $176.6682   $176.67   $176.65   $176.70  
  Purchase #2 $225.70   9.199%   $246.4621   $246.46   $246.45   $246.50  
  Purchase #3 $230.39   10.599%   $254.809   $254.81   $254.80   $254.80  
  Purchase #4 $203.37   5.206%   $213.9574   $213.96   $213.95   $214.00  
  Purchase #5 $41.41   5.241%   $43.5803   $43.58   $43.60   $43.60  
  Purchase #6 $140.38   8.495%   $152.3053   $152.31   $152.30   $152.30  
  Purchase #7 $16.39   13.283%   $18.5671   $18.57   $18.55   $18.60  
  7 purchase totals = $1,026.95       $1,106.3494   $1,106.36   $1,106.30   $1,106.50