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	$36.53	3.405%	$37.7738	$37.77	$37.75	$37.80
Purchase #2	$199.28	11.179%	$221.5575	$221.56	$221.55	$221.60
Purchase #3	$110.72	7.272%	$118.7716	$118.77	$118.75	$118.80
Purchase #4	$142.34	6.510%	$151.6063	$151.61	$151.60	$151.60
Purchase #5	$135.39	12.230%	$151.9482	$151.95	$151.95	$151.90
Purchase #6	$34.42	8.252%	$37.2603	$37.26	$37.25	$37.30
Purchase #7	$22.63	4.856%	$23.7289	$23.73	$23.75	$23.70
7 purchase totals =	$681.31		$742.6466	$742.65	$742.60	$742.70