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	$156.39	5.713%	$165.3246	$165.32	$165.30	$165.30
Purchase #2	$20.32	6.334%	$21.6071	$21.61	$21.60	$21.60
Purchase #3	$218.51	4.559%	$228.4719	$228.47	$228.45	$228.50
Purchase #4	$192.27	13.157%	$217.567	$217.57	$217.55	$217.60
Purchase #5	$137.93	6.154%	$146.4182	$146.42	$146.40	$146.40
Purchase #6	$167.74	10.830%	$185.9062	$185.91	$185.90	$185.90
Purchase #7	$204.46	11.277%	$227.517	$227.52	$227.50	$227.50
7 purchase totals =	$1,097.62		$1,192.8120	$1,192.82	$1,192.70	$1,192.80