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	$66.54	13.384%	$75.4457	$75.45	$75.45	$75.40
Purchase #2	$61.50	10.177%	$67.7589	$67.76	$67.75	$67.80
Purchase #3	$132.74	6.585%	$141.4809	$141.48	$141.50	$141.50
Purchase #4	$164.50	4.346%	$171.6492	$171.65	$171.65	$171.60
Purchase #5	$224.92	6.153%	$238.7593	$238.76	$238.75	$238.80
Purchase #6	$93.53	10.301%	$103.1645	$103.16	$103.15	$103.20
Purchase #7	$244.69	7.329%	$262.6233	$262.62	$262.60	$262.60
7 purchase totals =	$988.42		$1,060.8818	$1,060.88	$1,060.85	$1,060.90