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 $92.96   9.523%   $101.8126   $101.81   $101.80   $101.80  
  Purchase #2 $167.59   4.323%   $174.8349   $174.83   $174.85   $174.80  
  Purchase #3 $172.95   6.607%   $184.3768   $184.38   $184.40   $184.40  
  Purchase #4 $245.64   12.120%   $275.4116   $275.41   $275.40   $275.40  
  Purchase #5 $86.80   4.378%   $90.6001   $90.60   $90.60   $90.60  
  Purchase #6 $181.68   9.154%   $198.311   $198.31   $198.30   $198.30  
  Purchase #7 $202.73   4.592%   $212.0394   $212.04   $212.05   $212.00  
  7 purchase totals = $1,150.35       $1,237.3864   $1,237.38   $1,237.40   $1,237.30