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	$249.51	4.846%	$261.6013	$261.60	$261.60	$261.60
Purchase #2	$231.36	5.689%	$244.5221	$244.52	$244.50	$244.50
Purchase #3	$45.82	9.644%	$50.2389	$50.24	$50.25	$50.20
Purchase #4	$46.84	13.214%	$53.0294	$53.03	$53.05	$53.00
Purchase #5	$47.77	8.294%	$51.732	$51.73	$51.75	$51.70
Purchase #6	$196.77	13.784%	$223.8928	$223.89	$223.90	$223.90
Purchase #7	$243.36	3.489%	$251.8508	$251.85	$251.85	$251.90
7 purchase totals =	$1,061.43		$1,136.8673	$1,136.86	$1,136.90	$1,136.80