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	$176.62	4.806%	$185.1084	$185.11	$185.10	$185.10
Purchase #2	$113.67	5.647%	$120.0889	$120.09	$120.10	$120.10
Purchase #3	$148.66	10.175%	$163.7862	$163.79	$163.80	$163.80
Purchase #4	$196.63	13.136%	$222.4593	$222.46	$222.45	$222.50
Purchase #5	$99.67	11.744%	$111.3752	$111.38	$111.40	$111.40
Purchase #6	$215.67	4.104%	$224.5211	$224.52	$224.50	$224.50
Purchase #7	$204.73	11.467%	$228.2064	$228.21	$228.20	$228.20
7 purchase totals =	$1,155.65		$1,255.5455	$1,255.56	$1,255.55	$1,255.60