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	$144.80	11.583%	$161.5722	$161.57	$161.55	$161.60
Purchase #2	$130.70	12.281%	$146.7513	$146.75	$146.75	$146.80
Purchase #3	$145.32	3.335%	$150.1664	$150.17	$150.15	$150.20
Purchase #4	$42.25	9.424%	$46.2316	$46.23	$46.25	$46.20
Purchase #5	$87.49	13.339%	$99.1603	$99.16	$99.15	$99.20
Purchase #6	$226.45	8.846%	$246.4818	$246.48	$246.50	$246.50
Purchase #7	$76.84	7.428%	$82.5477	$82.55	$82.55	$82.50
7 purchase totals =	$853.85		$932.9113	$932.91	$932.90	$933.00