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	$31.59	11.121%	$35.1031	$35.10	$35.10	$35.10
Purchase #2	$18.33	10.395%	$20.2354	$20.24	$20.25	$20.20
Purchase #3	$55.63	9.274%	$60.7891	$60.79	$60.80	$60.80
Purchase #4	$106.82	4.412%	$111.5329	$111.53	$111.55	$111.50
Purchase #5	$47.77	13.271%	$54.1096	$54.11	$54.10	$54.10
Purchase #6	$51.26	11.250%	$57.0268	$57.03	$57.05	$57.00
Purchase #7	$194.48	6.827%	$207.7571	$207.76	$207.75	$207.80
7 purchase totals =	$505.88		$546.5540	$546.56	$546.60	$546.50