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	$118.99	5.374%	$125.3845	$125.38	$125.40	$125.40
Purchase #2	$153.86	7.781%	$165.8318	$165.83	$165.85	$165.80
Purchase #3	$39.25	10.668%	$43.4372	$43.44	$43.45	$43.40
Purchase #4	$72.41	11.145%	$80.4801	$80.48	$80.50	$80.50
Purchase #5	$48.33	10.820%	$53.5593	$53.56	$53.55	$53.60
Purchase #6	$32.39	7.439%	$34.7995	$34.80	$34.80	$34.80
Purchase #7	$132.28	13.422%	$150.0346	$150.03	$150.05	$150.00
7 purchase totals =	$597.51		$653.5270	$653.52	$653.60	$653.50