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	$100.80	5.634%	$106.4791	$106.48	$106.50	$106.50
Purchase #2	$27.81	13.238%	$31.4915	$31.49	$31.50	$31.50
Purchase #3	$106.26	12.597%	$119.6456	$119.65	$119.65	$119.60
Purchase #4	$183.52	9.188%	$200.3818	$200.38	$200.40	$200.40
Purchase #5	$247.65	13.671%	$281.5062	$281.51	$281.50	$281.50
Purchase #6	$167.72	4.133%	$174.6519	$174.65	$174.65	$174.70
Purchase #7	$136.50	11.858%	$152.6862	$152.69	$152.70	$152.70
7 purchase totals =	$970.26		$1,066.8423	$1,066.85	$1,066.90	$1,066.90