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	$172.90	8.176%	$187.0363	$187.04	$187.05	$187.00
Purchase #2	$180.75	5.469%	$190.6352	$190.64	$190.65	$190.60
Purchase #3	$50.81	6.277%	$53.9993	$54.00	$54.00	$54.00
Purchase #4	$245.60	4.804%	$257.3986	$257.40	$257.40	$257.40
Purchase #5	$127.75	4.155%	$133.058	$133.06	$133.05	$133.10
Purchase #6	$165.66	10.433%	$182.9433	$182.94	$182.95	$182.90
Purchase #7	$37.50	7.123%	$40.1711	$40.17	$40.15	$40.20
7 purchase totals =	$980.97		$1,045.2418	$1,045.25	$1,045.25	$1,045.20