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	$226.53	12.624%	$255.1271	$255.13	$255.15	$255.10
Purchase #2	$180.91	13.873%	$206.0076	$206.01	$206.00	$206.00
Purchase #3	$151.88	9.229%	$165.897	$165.90	$165.90	$165.90
Purchase #4	$174.57	9.526%	$191.1995	$191.20	$191.20	$191.20
Purchase #5	$54.78	4.390%	$57.1848	$57.18	$57.20	$57.20
Purchase #6	$218.27	5.113%	$229.4301	$229.43	$229.45	$229.40
Purchase #7	$192.28	9.513%	$210.5716	$210.57	$210.55	$210.60
7 purchase totals =	$1,199.22		$1,315.4177	$1,315.42	$1,315.45	$1,315.40