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	$58.71	6.510%	$62.532	$62.53	$62.55	$62.50
Purchase #2	$247.30	7.371%	$265.5285	$265.53	$265.55	$265.50
Purchase #3	$79.68	12.866%	$89.9316	$89.93	$89.95	$89.90
Purchase #4	$167.77	7.739%	$180.7537	$180.75	$180.75	$180.80
Purchase #5	$53.33	13.739%	$60.657	$60.66	$60.65	$60.70
Purchase #6	$133.35	11.361%	$148.4999	$148.50	$148.50	$148.50
Purchase #7	$80.77	3.567%	$83.6511	$83.65	$83.65	$83.70
7 purchase totals =	$820.91		$891.5538	$891.55	$891.60	$891.60