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	$98.72	8.632%	$107.2415	$107.24	$107.25	$107.20
Purchase #2	$59.93	9.863%	$65.8409	$65.84	$65.85	$65.80
Purchase #3	$150.56	7.588%	$161.9845	$161.98	$162.00	$162.00
Purchase #4	$203.59	12.804%	$229.6577	$229.66	$229.65	$229.70
Purchase #5	$77.46	7.797%	$83.4996	$83.50	$83.50	$83.50
Purchase #6	$132.91	13.558%	$150.9299	$150.93	$150.95	$150.90
Purchase #7	$84.72	5.561%	$89.4313	$89.43	$89.45	$89.40
7 purchase totals =	$807.89		$888.5854	$888.58	$888.65	$888.50