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	$90.69	9.125%	$98.9655	$98.97	$98.95	$99.00
Purchase #2	$146.37	12.381%	$164.4921	$164.49	$164.50	$164.50
Purchase #3	$184.88	5.288%	$194.6565	$194.66	$194.65	$194.70
Purchase #4	$78.79	8.540%	$85.5187	$85.52	$85.50	$85.50
Purchase #5	$110.93	11.495%	$123.6814	$123.68	$123.70	$123.70
Purchase #6	$120.33	13.514%	$136.5914	$136.59	$136.60	$136.60
Purchase #7	$244.47	10.674%	$270.5647	$270.56	$270.55	$270.60
7 purchase totals =	$976.46		$1,074.4703	$1,074.47	$1,074.45	$1,074.60