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	$123.90	7.519%	$133.216	$133.22	$133.20	$133.20
Purchase #2	$53.90	10.723%	$59.6797	$59.68	$59.70	$59.70
Purchase #3	$134.37	7.316%	$144.2005	$144.20	$144.20	$144.20
Purchase #4	$118.31	10.547%	$130.7882	$130.79	$130.80	$130.80
Purchase #5	$89.32	11.704%	$99.774	$99.77	$99.75	$99.80
Purchase #6	$69.82	13.390%	$79.1689	$79.17	$79.15	$79.20
Purchase #7	$59.78	11.867%	$66.8741	$66.87	$66.85	$66.90
7 purchase totals =	$649.40		$713.7014	$713.70	$713.65	$713.80