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	$130.43	13.346%	$147.8372	$147.84	$147.85	$147.80
Purchase #2	$139.52	4.168%	$145.3352	$145.34	$145.35	$145.30
Purchase #3	$196.59	3.659%	$203.7832	$203.78	$203.80	$203.80
Purchase #4	$90.30	4.678%	$94.5242	$94.52	$94.50	$94.50
Purchase #5	$115.30	7.240%	$123.6477	$123.65	$123.65	$123.60
Purchase #6	$54.59	10.193%	$60.1544	$60.15	$60.15	$60.20
Purchase #7	$85.66	9.208%	$93.5476	$93.55	$93.55	$93.50
7 purchase totals =	$812.39		$868.8295	$868.83	$868.85	$868.70