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	$231.95	5.335%	$244.3245	$244.32	$244.30	$244.30
Purchase #2	$19.77	10.626%	$21.8708	$21.87	$21.85	$21.90
Purchase #3	$39.90	13.608%	$45.3296	$45.33	$45.35	$45.30
Purchase #4	$183.53	3.202%	$189.4066	$189.41	$189.40	$189.40
Purchase #5	$76.76	7.697%	$82.6682	$82.67	$82.65	$82.70
Purchase #6	$135.86	13.734%	$154.519	$154.52	$154.50	$154.50
Purchase #7	$75.32	4.678%	$78.8435	$78.84	$78.85	$78.80
7 purchase totals =	$763.09		$816.9622	$816.96	$816.90	$816.90