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	$150.85	13.485%	$171.1921	$171.19	$171.20	$171.20
Purchase #2	$60.50	3.575%	$62.6629	$62.66	$62.65	$62.70
Purchase #3	$154.52	6.436%	$164.4649	$164.46	$164.45	$164.50
Purchase #4	$147.40	6.856%	$157.5057	$157.51	$157.50	$157.50
Purchase #5	$70.95	11.165%	$78.8716	$78.87	$78.85	$78.90
Purchase #6	$49.96	7.742%	$53.8279	$53.83	$53.85	$53.80
Purchase #7	$15.74	9.629%	$17.2556	$17.26	$17.25	$17.30
7 purchase totals =	$649.92		$705.7807	$705.78	$705.75	$705.90