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	$42.65	7.300%	$45.7635	$45.76	$45.75	$45.80
Purchase #2	$8.31	6.219%	$8.8268	$8.83	$8.85	$8.80
Purchase #3	$234.61	12.671%	$264.3374	$264.34	$264.35	$264.30
Purchase #4	$50.37	8.137%	$54.4686	$54.47	$54.45	$54.50
Purchase #5	$250.67	12.395%	$281.7405	$281.74	$281.75	$281.70
Purchase #6	$127.39	12.859%	$143.7711	$143.77	$143.75	$143.80
Purchase #7	$214.81	10.571%	$237.5176	$237.52	$237.50	$237.50
7 purchase totals =	$928.81		$1,036.4255	$1,036.43	$1,036.40	$1,036.40