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	$60.75	4.600%	$63.5445	$63.54	$63.55	$63.50
Purchase #2	$36.36	5.667%	$38.4205	$38.42	$38.40	$38.40
Purchase #3	$172.48	3.567%	$178.6324	$178.63	$178.65	$178.60
Purchase #4	$129.86	13.873%	$147.8755	$147.88	$147.90	$147.90
Purchase #5	$38.30	9.309%	$41.8653	$41.87	$41.85	$41.90
Purchase #6	$78.25	6.762%	$83.5413	$83.54	$83.55	$83.50
Purchase #7	$34.31	11.209%	$38.1558	$38.16	$38.15	$38.20
7 purchase totals =	$550.31		$592.0353	$592.04	$592.05	$592.00