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 $142.29   7.668%   $153.2008   $153.20   $153.20   $153.20  
  Purchase #2 $74.82   13.258%   $84.7396   $84.74   $84.75   $84.70  
  Purchase #3 $53.72   11.437%   $59.864   $59.86   $59.85   $59.90  
  Purchase #4 $185.61   3.145%   $191.4474   $191.45   $191.45   $191.40  
  Purchase #5 $238.60   3.130%   $246.0682   $246.07   $246.05   $246.10  
  Purchase #6 $196.45   4.553%   $205.3944   $205.39   $205.40   $205.40  
  Purchase #7 $135.36   11.743%   $151.2553   $151.26   $151.25   $151.30  
  7 purchase totals = $1,026.85       $1,091.9697   $1,091.97   $1,091.95   $1,092.00