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	$82.98	11.181%	$92.258	$92.26	$92.25	$92.30
Purchase #2	$243.31	11.292%	$270.7846	$270.78	$270.80	$270.80
Purchase #3	$144.59	11.861%	$161.7398	$161.74	$161.75	$161.70
Purchase #4	$184.43	8.679%	$200.4367	$200.44	$200.45	$200.40
Purchase #5	$224.51	13.654%	$255.1646	$255.16	$255.15	$255.20
Purchase #6	$17.32	12.333%	$19.4561	$19.46	$19.45	$19.50
Purchase #7	$72.66	7.855%	$78.3674	$78.37	$78.35	$78.40
7 purchase totals =	$969.80		$1,078.2072	$1,078.21	$1,078.20	$1,078.30