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	$166.76	8.754%	$181.3582	$181.36	$181.35	$181.40
Purchase #2	$164.71	11.169%	$183.1065	$183.11	$183.10	$183.10
Purchase #3	$99.75	3.532%	$103.2732	$103.27	$103.25	$103.30
Purchase #4	$111.59	5.332%	$117.54	$117.54	$117.55	$117.50
Purchase #5	$55.95	6.233%	$59.4374	$59.44	$59.45	$59.40
Purchase #6	$216.74	5.640%	$228.9641	$228.96	$228.95	$229.00
Purchase #7	$231.70	5.640%	$244.7679	$244.77	$244.75	$244.80
7 purchase totals =	$1,047.20		$1,118.4473	$1,118.45	$1,118.40	$1,118.50