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	$149.93	8.354%	$162.4552	$162.46	$162.45	$162.50
Purchase #2	$130.48	11.604%	$145.6209	$145.62	$145.60	$145.60
Purchase #3	$98.64	13.313%	$111.7719	$111.77	$111.75	$111.80
Purchase #4	$231.57	12.623%	$260.8011	$260.80	$260.80	$260.80
Purchase #5	$136.52	11.434%	$152.1297	$152.13	$152.15	$152.10
Purchase #6	$92.78	9.597%	$101.6841	$101.68	$101.70	$101.70
Purchase #7	$211.34	4.530%	$220.9137	$220.91	$220.90	$220.90
7 purchase totals =	$1,051.26		$1,155.3766	$1,155.37	$1,155.35	$1,155.40