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	$173.78	5.812%	$183.8801	$183.88	$183.90	$183.90
Purchase #2	$91.52	13.776%	$104.1278	$104.13	$104.15	$104.10
Purchase #3	$89.52	11.159%	$99.5095	$99.51	$99.50	$99.50
Purchase #4	$164.61	9.239%	$179.8183	$179.82	$179.80	$179.80
Purchase #5	$159.91	6.103%	$169.6693	$169.67	$169.65	$169.70
Purchase #6	$185.60	5.208%	$195.266	$195.27	$195.25	$195.30
Purchase #7	$175.50	3.230%	$181.1687	$181.17	$181.15	$181.20
7 purchase totals =	$1,040.44		$1,113.4397	$1,113.45	$1,113.40	$1,113.50