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	$127.51	12.874%	$143.9256	$143.93	$143.95	$143.90
Purchase #2	$138.70	10.445%	$153.1872	$153.19	$153.20	$153.20
Purchase #3	$29.73	6.286%	$31.5988	$31.60	$31.60	$31.60
Purchase #4	$250.31	5.502%	$264.0821	$264.08	$264.10	$264.10
Purchase #5	$96.50	5.261%	$101.5769	$101.58	$101.60	$101.60
Purchase #6	$95.66	4.562%	$100.024	$100.02	$100.00	$100.00
Purchase #7	$217.81	10.615%	$240.9305	$240.93	$240.95	$240.90
7 purchase totals =	$956.22		$1,035.3251	$1,035.33	$1,035.40	$1,035.30