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	$248.68	9.729%	$272.8741	$272.87	$272.85	$272.90
Purchase #2	$134.43	7.784%	$144.894	$144.89	$144.90	$144.90
Purchase #3	$173.34	10.643%	$191.7886	$191.79	$191.80	$191.80
Purchase #4	$23.63	5.108%	$24.837	$24.84	$24.85	$24.80
Purchase #5	$32.82	10.643%	$36.313	$36.31	$36.30	$36.30
Purchase #6	$54.96	8.371%	$59.5607	$59.56	$59.55	$59.60
Purchase #7	$60.66	10.235%	$66.8686	$66.87	$66.85	$66.90
7 purchase totals =	$728.52		$797.1360	$797.13	$797.10	$797.20