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	$125.78	9.388%	$137.5882	$137.59	$137.60	$137.60
Purchase #2	$42.42	7.414%	$45.565	$45.57	$45.55	$45.60
Purchase #3	$204.79	4.541%	$214.0895	$214.09	$214.10	$214.10
Purchase #4	$238.88	11.718%	$266.872	$266.87	$266.85	$266.90
Purchase #5	$58.54	3.163%	$60.3916	$60.39	$60.40	$60.40
Purchase #6	$215.39	5.611%	$227.4755	$227.48	$227.50	$227.50
Purchase #7	$175.94	12.612%	$198.1296	$198.13	$198.15	$198.10
7 purchase totals =	$1,061.74		$1,150.1114	$1,150.12	$1,150.15	$1,150.20