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	$112.32	13.805%	$127.8258	$127.83	$127.85	$127.80
Purchase #2	$89.34	3.135%	$92.1408	$92.14	$92.15	$92.10
Purchase #3	$218.93	5.721%	$231.455	$231.46	$231.45	$231.50
Purchase #4	$69.85	6.414%	$74.3302	$74.33	$74.35	$74.30
Purchase #5	$71.52	4.158%	$74.4938	$74.49	$74.50	$74.50
Purchase #6	$104.95	5.810%	$111.0476	$111.05	$111.05	$111.00
Purchase #7	$79.56	5.384%	$83.8435	$83.84	$83.85	$83.80
7 purchase totals =	$746.47		$795.1367	$795.14	$795.20	$795.00