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 $244.35   10.211%   $269.3006   $269.30   $269.30   $269.30  
  Purchase #2 $217.92   9.310%   $238.2084   $238.21   $238.20   $238.20  
  Purchase #3 $158.62   5.401%   $167.1871   $167.19   $167.20   $167.20  
  Purchase #4 $203.67   7.521%   $218.988   $218.99   $219.00   $219.00  
  Purchase #5 $10.30   9.806%   $11.31   $11.31   $11.30   $11.30  
  Purchase #6 $34.55   7.104%   $37.0044   $37.00   $37.00   $37.00  
  Purchase #7 $205.95   6.806%   $219.967   $219.97   $219.95   $220.00  
  7 purchase totals = $1,075.36       $1,161.9655   $1,161.97   $1,161.95   $1,162.00