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 $166.57   4.653%   $174.3205   $174.32   $174.30   $174.30  
  Purchase #2 $219.94   9.734%   $241.349   $241.35   $241.35   $241.30  
  Purchase #3 $23.59   10.474%   $26.0608   $26.06   $26.05   $26.10  
  Purchase #4 $240.44   4.679%   $251.6902   $251.69   $251.70   $251.70  
  Purchase #5 $204.99   6.639%   $218.5993   $218.60   $218.60   $218.60  
  Purchase #6 $57.88   10.573%   $63.9997   $64.00   $64.00   $64.00  
  Purchase #7 $233.88   4.728%   $244.9378   $244.94   $244.95   $244.90  
  7 purchase totals = $1,147.29       $1,220.9573   $1,220.96   $1,220.95   $1,220.90