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	$182.93	4.202%	$190.6167	$190.62	$190.60	$190.60
Purchase #2	$37.45	13.683%	$42.5743	$42.57	$42.55	$42.60
Purchase #3	$148.32	11.581%	$165.4969	$165.50	$165.50	$165.50
Purchase #4	$22.55	12.206%	$25.3025	$25.30	$25.30	$25.30
Purchase #5	$12.34	10.644%	$13.6535	$13.65	$13.65	$13.70
Purchase #6	$175.92	13.722%	$200.0597	$200.06	$200.05	$200.10
Purchase #7	$183.61	8.308%	$198.8643	$198.86	$198.85	$198.90
7 purchase totals =	$763.12		$836.5679	$836.56	$836.50	$836.70