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	$159.34	9.510%	$174.4932	$174.49	$174.50	$174.50
Purchase #2	$73.83	10.856%	$81.845	$81.85	$81.85	$81.80
Purchase #3	$102.92	7.762%	$110.9087	$110.91	$110.90	$110.90
Purchase #4	$248.30	4.819%	$260.2656	$260.27	$260.25	$260.30
Purchase #5	$232.27	9.502%	$254.3403	$254.34	$254.35	$254.30
Purchase #6	$190.42	3.315%	$196.7324	$196.73	$196.75	$196.70
Purchase #7	$77.96	13.428%	$88.4285	$88.43	$88.45	$88.40
7 purchase totals =	$1,085.04		$1,167.0137	$1,167.02	$1,167.05	$1,166.90