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	$167.74	7.647%	$180.5671	$180.57	$180.55	$180.60
Purchase #2	$231.88	13.323%	$262.7734	$262.77	$262.75	$262.80
Purchase #3	$202.28	6.818%	$216.0715	$216.07	$216.05	$216.10
Purchase #4	$141.74	11.675%	$158.2881	$158.29	$158.30	$158.30
Purchase #5	$39.42	8.853%	$42.9099	$42.91	$42.90	$42.90
Purchase #6	$148.38	10.599%	$164.1068	$164.11	$164.10	$164.10
Purchase #7	$160.80	9.143%	$175.5019	$175.50	$175.50	$175.50
7 purchase totals =	$1,092.24		$1,200.2187	$1,200.22	$1,200.15	$1,200.30