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	$175.82	12.594%	$197.9628	$197.96	$197.95	$198.00
Purchase #2	$248.78	11.822%	$278.1908	$278.19	$278.20	$278.20
Purchase #3	$57.90	6.224%	$61.5037	$61.50	$61.50	$61.50
Purchase #4	$96.38	4.694%	$100.9041	$100.90	$100.90	$100.90
Purchase #5	$31.58	12.555%	$35.5449	$35.54	$35.55	$35.50
Purchase #6	$155.28	6.634%	$165.5813	$165.58	$165.60	$165.60
Purchase #7	$249.26	9.181%	$272.1446	$272.14	$272.15	$272.10
7 purchase totals =	$1,015.00		$1,111.8322	$1,111.81	$1,111.85	$1,111.80