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	$184.35	4.869%	$193.326	$193.33	$193.35	$193.30
Purchase #2	$99.88	11.639%	$111.505	$111.51	$111.50	$111.50
Purchase #3	$134.94	7.625%	$145.2292	$145.23	$145.25	$145.20
Purchase #4	$238.99	4.768%	$250.385	$250.39	$250.40	$250.40
Purchase #5	$96.97	12.378%	$108.9729	$108.97	$108.95	$109.00
Purchase #6	$36.26	11.709%	$40.5057	$40.51	$40.50	$40.50
Purchase #7	$9.94	8.301%	$10.7651	$10.77	$10.75	$10.80
7 purchase totals =	$801.33		$860.6889	$860.71	$860.70	$860.70