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 $48.68   10.288%   $53.6882   $53.69   $53.70   $53.70  
  Purchase #2 $208.72   8.585%   $226.6386   $226.64   $226.65   $226.60  
  Purchase #3 $79.48   6.568%   $84.7002   $84.70   $84.70   $84.70  
  Purchase #4 $231.65   4.117%   $241.187   $241.19   $241.20   $241.20  
  Purchase #5 $229.42   4.820%   $240.478   $240.48   $240.50   $240.50  
  Purchase #6 $181.72   11.527%   $202.6669   $202.67   $202.65   $202.70  
  Purchase #7 $69.59   8.220%   $75.3103   $75.31   $75.30   $75.30  
  7 purchase totals = $1,049.26       $1,124.6692   $1,124.68   $1,124.70   $1,124.70