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	$31.84	11.161%	$35.3937	$35.39	$35.40	$35.40
Purchase #2	$158.88	4.194%	$165.5434	$165.54	$165.55	$165.50
Purchase #3	$218.68	11.326%	$243.4477	$243.45	$243.45	$243.40
Purchase #4	$87.33	7.794%	$94.1365	$94.14	$94.15	$94.10
Purchase #5	$27.76	5.824%	$29.3767	$29.38	$29.40	$29.40
Purchase #6	$67.59	4.264%	$70.472	$70.47	$70.45	$70.50
Purchase #7	$50.70	13.341%	$57.4639	$57.46	$57.45	$57.50
7 purchase totals =	$642.78		$695.8339	$695.83	$695.85	$695.80