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	$224.78	13.681%	$255.5322	$255.53	$255.55	$255.50
Purchase #2	$96.77	7.816%	$104.3335	$104.33	$104.35	$104.30
Purchase #3	$139.65	13.469%	$158.4595	$158.46	$158.45	$158.50
Purchase #4	$83.49	10.409%	$92.1805	$92.18	$92.20	$92.20
Purchase #5	$118.26	5.113%	$124.3066	$124.31	$124.30	$124.30
Purchase #6	$188.82	11.575%	$210.6759	$210.68	$210.70	$210.70
Purchase #7	$191.26	3.737%	$198.4074	$198.41	$198.40	$198.40
7 purchase totals =	$1,043.03		$1,143.8956	$1,143.90	$1,143.95	$1,143.90