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	$113.62	3.433%	$117.5206	$117.52	$117.50	$117.50
Purchase #2	$233.86	9.850%	$256.8952	$256.90	$256.90	$256.90
Purchase #3	$143.97	3.862%	$149.5301	$149.53	$149.55	$149.50
Purchase #4	$171.33	8.528%	$185.941	$185.94	$185.95	$185.90
Purchase #5	$180.31	13.831%	$205.2487	$205.25	$205.25	$205.20
Purchase #6	$147.81	13.476%	$167.7289	$167.73	$167.75	$167.70
Purchase #7	$20.58	11.434%	$22.9331	$22.93	$22.95	$22.90
7 purchase totals =	$1,011.48		$1,105.7976	$1,105.80	$1,105.85	$1,105.60