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	$180.55	4.410%	$188.5123	$188.51	$188.50	$188.50
Purchase #2	$96.39	6.215%	$102.3806	$102.38	$102.40	$102.40
Purchase #3	$37.55	5.483%	$39.6089	$39.61	$39.60	$39.60
Purchase #4	$238.65	5.417%	$251.5777	$251.58	$251.60	$251.60
Purchase #5	$244.74	4.689%	$256.2159	$256.22	$256.20	$256.20
Purchase #6	$87.97	6.111%	$93.3458	$93.35	$93.35	$93.30
Purchase #7	$172.46	13.443%	$195.6438	$195.64	$195.65	$195.60
7 purchase totals =	$1,058.31		$1,127.2850	$1,127.29	$1,127.30	$1,127.20