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	$30.84	4.582%	$32.2531	$32.25	$32.25	$32.30
Purchase #2	$155.31	13.209%	$175.8249	$175.82	$175.80	$175.80
Purchase #3	$248.48	6.448%	$264.502	$264.50	$264.50	$264.50
Purchase #4	$66.27	12.271%	$74.402	$74.40	$74.40	$74.40
Purchase #5	$236.54	7.451%	$254.1646	$254.16	$254.15	$254.20
Purchase #6	$65.64	9.286%	$71.7353	$71.74	$71.75	$71.70
Purchase #7	$241.85	12.219%	$271.4017	$271.40	$271.40	$271.40
7 purchase totals =	$1,044.93		$1,144.2836	$1,144.27	$1,144.25	$1,144.30