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	$48.29	11.874%	$54.024	$54.02	$54.00	$54.00
Purchase #2	$64.50	12.104%	$72.3071	$72.31	$72.30	$72.30
Purchase #3	$245.60	13.160%	$277.921	$277.92	$277.90	$277.90
Purchase #4	$174.95	9.544%	$191.6472	$191.65	$191.65	$191.60
Purchase #5	$243.70	4.191%	$253.9135	$253.91	$253.90	$253.90
Purchase #6	$186.68	8.781%	$203.0724	$203.07	$203.05	$203.10
Purchase #7	$26.89	6.269%	$28.5757	$28.58	$28.60	$28.60
7 purchase totals =	$990.61		$1,081.4609	$1,081.46	$1,081.40	$1,081.40