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	$138.29	4.650%	$144.7205	$144.72	$144.70	$144.70
Purchase #2	$141.42	3.318%	$146.1123	$146.11	$146.10	$146.10
Purchase #3	$52.42	3.268%	$54.1331	$54.13	$54.15	$54.10
Purchase #4	$151.73	13.658%	$172.4533	$172.45	$172.45	$172.50
Purchase #5	$145.40	3.673%	$150.7405	$150.74	$150.75	$150.70
Purchase #6	$161.63	13.472%	$183.4048	$183.40	$183.40	$183.40
Purchase #7	$92.38	9.812%	$101.4443	$101.44	$101.45	$101.40
7 purchase totals =	$883.27		$953.0088	$952.99	$953.00	$952.90