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	$229.78	6.508%	$244.7341	$244.73	$244.75	$244.70
Purchase #2	$101.37	11.193%	$112.7163	$112.72	$112.70	$112.70
Purchase #3	$37.84	13.222%	$42.8432	$42.84	$42.85	$42.80
Purchase #4	$89.53	7.826%	$96.5366	$96.54	$96.55	$96.50
Purchase #5	$229.37	10.351%	$253.1121	$253.11	$253.10	$253.10
Purchase #6	$122.27	3.137%	$126.1056	$126.11	$126.10	$126.10
Purchase #7	$82.56	8.697%	$89.7402	$89.74	$89.75	$89.70
7 purchase totals =	$892.72		$965.7881	$965.79	$965.80	$965.60