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	$106.35	4.713%	$111.3623	$111.36	$111.35	$111.40
Purchase #2	$201.53	8.236%	$218.128	$218.13	$218.15	$218.10
Purchase #3	$240.25	5.572%	$253.6367	$253.64	$253.65	$253.60
Purchase #4	$217.84	11.231%	$242.3056	$242.31	$242.30	$242.30
Purchase #5	$219.40	4.447%	$229.1567	$229.16	$229.15	$229.20
Purchase #6	$172.89	10.192%	$190.5109	$190.51	$190.50	$190.50
Purchase #7	$49.45	7.658%	$53.2369	$53.24	$53.25	$53.20
7 purchase totals =	$1,207.71		$1,298.3371	$1,298.35	$1,298.35	$1,298.30