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	$162.53	10.649%	$179.8378	$179.84	$179.85	$179.80
Purchase #2	$190.65	8.785%	$207.3986	$207.40	$207.40	$207.40
Purchase #3	$57.63	12.380%	$64.7646	$64.76	$64.75	$64.80
Purchase #4	$145.39	3.327%	$150.2271	$150.23	$150.25	$150.20
Purchase #5	$226.56	12.772%	$255.4962	$255.50	$255.50	$255.50
Purchase #6	$22.58	11.319%	$25.1358	$25.14	$25.15	$25.10
Purchase #7	$53.52	11.501%	$59.6753	$59.68	$59.70	$59.70
7 purchase totals =	$858.86		$942.5354	$942.55	$942.60	$942.50