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	$109.85	8.215%	$118.8742	$118.87	$118.85	$118.90
Purchase #2	$213.95	4.647%	$223.8923	$223.89	$223.90	$223.90
Purchase #3	$48.49	11.700%	$54.1633	$54.16	$54.15	$54.20
Purchase #4	$149.30	9.456%	$163.4178	$163.42	$163.40	$163.40
Purchase #5	$38.76	4.138%	$40.3639	$40.36	$40.35	$40.40
Purchase #6	$53.87	10.672%	$59.619	$59.62	$59.60	$59.60
Purchase #7	$69.52	13.323%	$78.7821	$78.78	$78.80	$78.80
7 purchase totals =	$683.74		$739.1126	$739.10	$739.05	$739.20