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	$149.78	7.145%	$160.4818	$160.48	$160.50	$160.50
Purchase #2	$174.90	12.783%	$197.2575	$197.26	$197.25	$197.30
Purchase #3	$249.73	12.710%	$281.4707	$281.47	$281.45	$281.50
Purchase #4	$152.66	4.816%	$160.0121	$160.01	$160.00	$160.00
Purchase #5	$228.91	11.665%	$255.6124	$255.61	$255.60	$255.60
Purchase #6	$196.52	12.795%	$221.6647	$221.66	$221.65	$221.70
Purchase #7	$154.48	9.283%	$168.8204	$168.82	$168.80	$168.80
7 purchase totals =	$1,306.98		$1,445.3196	$1,445.31	$1,445.25	$1,445.40