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	$20.72	9.103%	$22.6061	$22.61	$22.60	$22.60
Purchase #2	$25.63	13.600%	$29.1157	$29.12	$29.10	$29.10
Purchase #3	$172.63	6.660%	$184.1272	$184.13	$184.15	$184.10
Purchase #4	$72.78	5.695%	$76.9248	$76.92	$76.90	$76.90
Purchase #5	$46.51	9.854%	$51.0931	$51.09	$51.10	$51.10
Purchase #6	$98.87	6.444%	$105.2412	$105.24	$105.25	$105.20
Purchase #7	$250.69	11.469%	$279.4416	$279.44	$279.45	$279.40
7 purchase totals =	$687.83		$748.5497	$748.55	$748.55	$748.40