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	$130.70	11.499%	$145.7292	$145.73	$145.75	$145.70
Purchase #2	$151.50	8.431%	$164.273	$164.27	$164.25	$164.30
Purchase #3	$223.82	5.236%	$235.5392	$235.54	$235.55	$235.50
Purchase #4	$168.49	8.555%	$182.9043	$182.90	$182.90	$182.90
Purchase #5	$9.65	6.772%	$10.3035	$10.30	$10.30	$10.30
Purchase #6	$243.45	13.192%	$275.5659	$275.57	$275.55	$275.60
Purchase #7	$86.71	4.117%	$90.2799	$90.28	$90.30	$90.30
7 purchase totals =	$1,014.32		$1,104.5950	$1,104.59	$1,104.60	$1,104.60