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	$207.38	7.828%	$223.6137	$223.61	$223.60	$223.60
Purchase #2	$69.77	8.264%	$75.5358	$75.54	$75.55	$75.50
Purchase #3	$137.56	9.606%	$150.774	$150.77	$150.75	$150.80
Purchase #4	$59.67	11.271%	$66.3954	$66.40	$66.40	$66.40
Purchase #5	$127.61	7.238%	$136.8464	$136.85	$136.85	$136.80
Purchase #6	$47.89	4.837%	$50.2064	$50.21	$50.20	$50.20
Purchase #7	$41.38	3.477%	$42.8188	$42.82	$42.80	$42.80
7 purchase totals =	$691.26		$746.1905	$746.20	$746.15	$746.10