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	$217.83	3.346%	$225.1186	$225.12	$225.10	$225.10
Purchase #2	$97.41	5.815%	$103.0744	$103.07	$103.05	$103.10
Purchase #3	$55.45	9.166%	$60.5325	$60.53	$60.55	$60.50
Purchase #4	$9.70	8.540%	$10.5284	$10.53	$10.55	$10.50
Purchase #5	$120.40	6.425%	$128.1357	$128.14	$128.15	$128.10
Purchase #6	$241.82	4.164%	$251.8894	$251.89	$251.90	$251.90
Purchase #7	$213.58	11.626%	$238.4108	$238.41	$238.40	$238.40
7 purchase totals =	$956.19		$1,017.6898	$1,017.69	$1,017.70	$1,017.60