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	$149.30	8.862%	$162.531	$162.53	$162.55	$162.50
Purchase #2	$123.33	13.244%	$139.6638	$139.66	$139.65	$139.70
Purchase #3	$238.75	4.548%	$249.6084	$249.61	$249.60	$249.60
Purchase #4	$88.86	12.513%	$99.9791	$99.98	$100.00	$100.00
Purchase #5	$141.90	11.194%	$157.7843	$157.78	$157.80	$157.80
Purchase #6	$140.76	4.753%	$147.4503	$147.45	$147.45	$147.50
Purchase #7	$38.53	13.433%	$43.7057	$43.71	$43.70	$43.70
7 purchase totals =	$921.43		$1,000.7226	$1,000.72	$1,000.75	$1,000.80