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	$89.48	4.472%	$93.4815	$93.48	$93.50	$93.50
Purchase #2	$48.52	11.314%	$54.0096	$54.01	$54.00	$54.00
Purchase #3	$93.59	7.579%	$100.6832	$100.68	$100.70	$100.70
Purchase #4	$143.88	11.834%	$160.9068	$160.91	$160.90	$160.90
Purchase #5	$112.47	13.594%	$127.7592	$127.76	$127.75	$127.80
Purchase #6	$15.97	5.282%	$16.8135	$16.81	$16.80	$16.80
Purchase #7	$236.71	11.353%	$263.5837	$263.58	$263.60	$263.60
7 purchase totals =	$740.62		$817.2375	$817.23	$817.25	$817.30