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	$41.89	9.693%	$45.9504	$45.95	$45.95	$46.00
Purchase #2	$75.76	6.388%	$80.5995	$80.60	$80.60	$80.60
Purchase #3	$66.93	7.173%	$71.7309	$71.73	$71.75	$71.70
Purchase #4	$222.66	9.873%	$244.6432	$244.64	$244.65	$244.60
Purchase #5	$201.37	7.408%	$216.2875	$216.29	$216.30	$216.30
Purchase #6	$169.92	7.631%	$182.8866	$182.89	$182.90	$182.90
Purchase #7	$244.74	5.201%	$257.4689	$257.47	$257.45	$257.50
7 purchase totals =	$1,023.27		$1,099.5670	$1,099.57	$1,099.60	$1,099.60