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	$112.45	13.602%	$127.7454	$127.75	$127.75	$127.70
Purchase #2	$148.45	11.372%	$165.3317	$165.33	$165.35	$165.30
Purchase #3	$164.69	4.204%	$171.6136	$171.61	$171.60	$171.60
Purchase #4	$11.99	10.474%	$13.2458	$13.25	$13.25	$13.20
Purchase #5	$134.52	13.633%	$152.8591	$152.86	$152.85	$152.90
Purchase #6	$131.71	13.262%	$149.1774	$149.18	$149.20	$149.20
Purchase #7	$121.66	6.300%	$129.3246	$129.32	$129.30	$129.30
7 purchase totals =	$825.47		$909.2976	$909.30	$909.30	$909.20