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	$82.60	9.163%	$90.1686	$90.17	$90.15	$90.20
Purchase #2	$36.48	3.811%	$37.8703	$37.87	$37.85	$37.90
Purchase #3	$166.26	6.425%	$176.9422	$176.94	$176.95	$176.90
Purchase #4	$231.25	5.298%	$243.5016	$243.50	$243.50	$243.50
Purchase #5	$202.53	12.368%	$227.5789	$227.58	$227.60	$227.60
Purchase #6	$25.74	4.439%	$26.8826	$26.88	$26.90	$26.90
Purchase #7	$96.96	6.322%	$103.0898	$103.09	$103.10	$103.10
7 purchase totals =	$841.82		$906.0340	$906.03	$906.05	$906.10