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	$161.75	7.299%	$173.5561	$173.56	$173.55	$173.60
Purchase #2	$46.54	11.521%	$51.9019	$51.90	$51.90	$51.90
Purchase #3	$154.35	4.240%	$160.8944	$160.89	$160.90	$160.90
Purchase #4	$54.64	13.485%	$62.0082	$62.01	$62.00	$62.00
Purchase #5	$64.26	3.223%	$66.3311	$66.33	$66.35	$66.30
Purchase #6	$154.61	3.543%	$160.0878	$160.09	$160.10	$160.10
Purchase #7	$35.53	4.319%	$37.0645	$37.06	$37.05	$37.10
7 purchase totals =	$671.68		$711.8440	$711.84	$711.85	$711.90