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	$169.48	12.265%	$190.2667	$190.27	$190.25	$190.30
Purchase #2	$219.60	5.333%	$231.3113	$231.31	$231.30	$231.30
Purchase #3	$59.74	3.242%	$61.6768	$61.68	$61.70	$61.70
Purchase #4	$139.96	13.237%	$158.4865	$158.49	$158.50	$158.50
Purchase #5	$167.95	12.578%	$189.0748	$189.07	$189.05	$189.10
Purchase #6	$28.75	8.710%	$31.2541	$31.25	$31.25	$31.30
Purchase #7	$87.41	4.227%	$91.1048	$91.10	$91.10	$91.10
7 purchase totals =	$872.89		$953.1750	$953.17	$953.15	$953.30