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	$211.75	13.776%	$240.9207	$240.92	$240.90	$240.90
Purchase #2	$76.92	7.382%	$82.5982	$82.60	$82.60	$82.60
Purchase #3	$52.34	4.552%	$54.7225	$54.72	$54.70	$54.70
Purchase #4	$143.79	10.615%	$159.0533	$159.05	$159.05	$159.10
Purchase #5	$47.39	7.158%	$50.7822	$50.78	$50.80	$50.80
Purchase #6	$90.62	8.436%	$98.2647	$98.26	$98.25	$98.30
Purchase #7	$188.53	4.478%	$196.9724	$196.97	$196.95	$197.00
7 purchase totals =	$811.34		$883.3140	$883.30	$883.25	$883.40