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	$250.73	4.464%	$261.9226	$261.92	$261.90	$261.90
Purchase #2	$149.68	5.572%	$158.0202	$158.02	$158.00	$158.00
Purchase #3	$59.74	11.520%	$66.622	$66.62	$66.60	$66.60
Purchase #4	$54.66	13.259%	$61.9074	$61.91	$61.90	$61.90
Purchase #5	$48.85	4.303%	$50.952	$50.95	$50.95	$51.00
Purchase #6	$221.54	12.245%	$248.6676	$248.67	$248.65	$248.70
Purchase #7	$175.62	7.570%	$188.9144	$188.91	$188.90	$188.90
7 purchase totals =	$960.82		$1,037.0062	$1,037.00	$1,036.90	$1,037.00