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	$32.59	12.718%	$36.7348	$36.73	$36.75	$36.70
Purchase #2	$33.26	13.678%	$37.8093	$37.81	$37.80	$37.80
Purchase #3	$144.50	4.759%	$151.3768	$151.38	$151.40	$151.40
Purchase #4	$191.27	13.182%	$216.4832	$216.48	$216.50	$216.50
Purchase #5	$158.94	3.762%	$164.9193	$164.92	$164.90	$164.90
Purchase #6	$48.25	11.230%	$53.6685	$53.67	$53.65	$53.70
Purchase #7	$77.73	10.295%	$85.7323	$85.73	$85.75	$85.70
7 purchase totals =	$686.54		$746.7242	$746.72	$746.75	$746.70