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	$106.64	5.162%	$112.1448	$112.14	$112.15	$112.10
Purchase #2	$57.33	6.203%	$60.8862	$60.89	$60.90	$60.90
Purchase #3	$244.30	10.178%	$269.1649	$269.16	$269.15	$269.20
Purchase #4	$102.38	4.184%	$106.6636	$106.66	$106.65	$106.70
Purchase #5	$151.52	7.175%	$162.3916	$162.39	$162.40	$162.40
Purchase #6	$64.89	3.689%	$67.2838	$67.28	$67.30	$67.30
Purchase #7	$140.50	11.303%	$156.3807	$156.38	$156.40	$156.40
7 purchase totals =	$867.56		$934.9156	$934.90	$934.95	$935.00