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	$57.26	4.322%	$59.7348	$59.73	$59.75	$59.70
Purchase #2	$156.74	13.464%	$177.8435	$177.84	$177.85	$177.80
Purchase #3	$51.83	5.388%	$54.6226	$54.62	$54.60	$54.60
Purchase #4	$8.32	12.712%	$9.3776	$9.38	$9.40	$9.40
Purchase #5	$230.90	5.634%	$243.9089	$243.91	$243.90	$243.90
Purchase #6	$58.56	4.333%	$61.0974	$61.10	$61.10	$61.10
Purchase #7	$39.31	10.198%	$43.3188	$43.32	$43.30	$43.30
7 purchase totals =	$602.92		$649.9036	$649.90	$649.90	$649.80