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	$131.42	12.785%	$148.222	$148.22	$148.20	$148.20
Purchase #2	$104.51	6.563%	$111.369	$111.37	$111.35	$111.40
Purchase #3	$141.65	7.386%	$152.1123	$152.11	$152.10	$152.10
Purchase #4	$152.98	4.447%	$159.783	$159.78	$159.80	$159.80
Purchase #5	$48.40	4.671%	$50.6608	$50.66	$50.65	$50.70
Purchase #6	$197.82	7.402%	$212.4626	$212.46	$212.45	$212.50
Purchase #7	$158.51	7.452%	$170.3222	$170.32	$170.30	$170.30
7 purchase totals =	$935.29		$1,004.9319	$1,004.92	$1,004.85	$1,005.00