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	$44.38	3.386%	$45.8827	$45.88	$45.90	$45.90
Purchase #2	$230.33	11.224%	$256.1822	$256.18	$256.20	$256.20
Purchase #3	$47.26	3.276%	$48.8082	$48.81	$48.80	$48.80
Purchase #4	$64.32	11.451%	$71.6853	$71.69	$71.70	$71.70
Purchase #5	$73.52	6.462%	$78.2709	$78.27	$78.25	$78.30
Purchase #6	$29.79	5.765%	$31.5074	$31.51	$31.50	$31.50
Purchase #7	$80.74	10.810%	$89.468	$89.47	$89.45	$89.50
7 purchase totals =	$570.34		$621.8047	$621.81	$621.80	$621.90