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	$52.64	3.379%	$54.4187	$54.42	$54.40	$54.40
Purchase #2	$16.67	10.694%	$18.4527	$18.45	$18.45	$18.50
Purchase #3	$154.27	6.399%	$164.1417	$164.14	$164.15	$164.10
Purchase #4	$129.41	7.222%	$138.756	$138.76	$138.75	$138.80
Purchase #5	$35.74	4.509%	$37.3515	$37.35	$37.35	$37.40
Purchase #6	$173.27	9.321%	$189.4205	$189.42	$189.40	$189.40
Purchase #7	$167.69	8.790%	$182.43	$182.43	$182.45	$182.40
7 purchase totals =	$729.69		$784.9711	$784.97	$784.95	$785.00