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 $58.56   5.189%   $61.5987   $61.60   $61.60   $61.60  
  Purchase #2 $166.64   10.598%   $184.3005   $184.30   $184.30   $184.30  
  Purchase #3 $192.74   9.662%   $211.3625   $211.36   $211.35   $211.40  
  Purchase #4 $87.84   3.833%   $91.2069   $91.21   $91.20   $91.20  
  Purchase #5 $39.77   13.744%   $45.236   $45.24   $45.25   $45.20  
  Purchase #6 $223.60   6.651%   $238.4716   $238.47   $238.45   $238.50  
  Purchase #7 $219.65   8.525%   $238.3752   $238.38   $238.40   $238.40  
  7 purchase totals = $988.80       $1,070.5514   $1,070.56   $1,070.55   $1,070.60