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	$41.26	12.386%	$46.3705	$46.37	$46.35	$46.40
Purchase #2	$111.51	7.123%	$119.4529	$119.45	$119.45	$119.50
Purchase #3	$168.55	3.415%	$174.306	$174.31	$174.30	$174.30
Purchase #4	$179.66	9.512%	$196.7493	$196.75	$196.75	$196.70
Purchase #5	$100.97	4.156%	$105.1663	$105.17	$105.15	$105.20
Purchase #6	$223.90	12.405%	$251.6748	$251.67	$251.65	$251.70
Purchase #7	$99.41	13.249%	$112.5808	$112.58	$112.60	$112.60
7 purchase totals =	$925.26		$1,006.3006	$1,006.30	$1,006.25	$1,006.40