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	$101.74	9.375%	$111.2781	$111.28	$111.30	$111.30
Purchase #2	$51.54	13.587%	$58.5427	$58.54	$58.55	$58.50
Purchase #3	$21.79	3.707%	$22.5978	$22.60	$22.60	$22.60
Purchase #4	$181.53	5.727%	$191.9262	$191.93	$191.95	$191.90
Purchase #5	$208.37	11.102%	$231.5032	$231.50	$231.50	$231.50
Purchase #6	$27.29	9.512%	$29.8858	$29.89	$29.90	$29.90
Purchase #7	$96.56	5.742%	$102.1045	$102.10	$102.10	$102.10
7 purchase totals =	$688.82		$747.8383	$747.84	$747.90	$747.80