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	$160.69	7.437%	$172.6405	$172.64	$172.65	$172.60
Purchase #2	$113.81	11.641%	$127.0586	$127.06	$127.05	$127.10
Purchase #3	$101.72	6.674%	$108.5088	$108.51	$108.50	$108.50
Purchase #4	$67.84	11.768%	$75.8234	$75.82	$75.80	$75.80
Purchase #5	$59.56	5.391%	$62.7709	$62.77	$62.75	$62.80
Purchase #6	$35.42	3.742%	$36.7454	$36.75	$36.75	$36.70
Purchase #7	$33.50	13.518%	$38.0285	$38.03	$38.05	$38.00
7 purchase totals =	$572.54		$621.5761	$621.58	$621.55	$621.50