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	$139.44	5.795%	$147.5205	$147.52	$147.50	$147.50
Purchase #2	$165.40	8.619%	$179.6558	$179.66	$179.65	$179.70
Purchase #3	$197.71	7.352%	$212.2456	$212.25	$212.25	$212.20
Purchase #4	$40.62	11.730%	$45.3847	$45.38	$45.40	$45.40
Purchase #5	$48.25	4.780%	$50.5564	$50.56	$50.55	$50.60
Purchase #6	$83.65	10.668%	$92.5738	$92.57	$92.55	$92.60
Purchase #7	$22.39	9.179%	$24.4452	$24.45	$24.45	$24.40
7 purchase totals =	$697.46		$752.3820	$752.39	$752.35	$752.40