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	$131.28	13.661%	$149.2142	$149.21	$149.20	$149.20
Purchase #2	$71.36	10.450%	$78.8171	$78.82	$78.80	$78.80
Purchase #3	$227.58	11.447%	$253.6311	$253.63	$253.65	$253.60
Purchase #4	$40.98	13.532%	$46.5254	$46.53	$46.55	$46.50
Purchase #5	$153.43	11.680%	$171.3506	$171.35	$171.35	$171.40
Purchase #6	$149.37	10.495%	$165.0464	$165.05	$165.05	$165.00
Purchase #7	$27.71	6.495%	$29.5098	$29.51	$29.50	$29.50
7 purchase totals =	$801.71		$894.0946	$894.10	$894.10	$894.00