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	$185.28	10.781%	$205.255	$205.26	$205.25	$205.30
Purchase #2	$239.30	6.862%	$255.7208	$255.72	$255.70	$255.70
Purchase #3	$155.53	6.548%	$165.7141	$165.71	$165.70	$165.70
Purchase #4	$70.57	11.658%	$78.7971	$78.80	$78.80	$78.80
Purchase #5	$134.96	3.815%	$140.1087	$140.11	$140.10	$140.10
Purchase #6	$160.42	7.114%	$171.8323	$171.83	$171.85	$171.80
Purchase #7	$45.29	12.622%	$51.0065	$51.01	$51.00	$51.00
7 purchase totals =	$991.35		$1,068.4345	$1,068.44	$1,068.40	$1,068.40