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	$58.34	10.818%	$64.6512	$64.65	$64.65	$64.70
Purchase #2	$48.63	13.478%	$55.1844	$55.18	$55.20	$55.20
Purchase #3	$96.59	9.492%	$105.7583	$105.76	$105.75	$105.80
Purchase #4	$80.35	13.381%	$91.1016	$91.10	$91.10	$91.10
Purchase #5	$242.68	13.850%	$276.2912	$276.29	$276.30	$276.30
Purchase #6	$118.32	7.354%	$127.0213	$127.02	$127.00	$127.00
Purchase #7	$150.34	3.371%	$155.408	$155.41	$155.40	$155.40
7 purchase totals =	$795.25		$875.4160	$875.41	$875.40	$875.50