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	$112.38	7.606%	$120.9276	$120.93	$120.95	$120.90
Purchase #2	$10.30	11.327%	$11.4667	$11.47	$11.45	$11.50
Purchase #3	$82.57	4.512%	$86.2956	$86.30	$86.30	$86.30
Purchase #4	$128.25	3.643%	$132.9221	$132.92	$132.90	$132.90
Purchase #5	$68.87	5.606%	$72.7309	$72.73	$72.75	$72.70
Purchase #6	$42.37	10.202%	$46.6926	$46.69	$46.70	$46.70
Purchase #7	$202.58	13.303%	$229.5292	$229.53	$229.55	$229.50
7 purchase totals =	$647.32		$700.5647	$700.57	$700.60	$700.50