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	$65.98	10.139%	$72.6697	$72.67	$72.65	$72.70
Purchase #2	$126.92	11.267%	$141.2201	$141.22	$141.20	$141.20
Purchase #3	$95.39	4.871%	$100.0364	$100.04	$100.05	$100.00
Purchase #4	$86.95	12.853%	$98.1257	$98.13	$98.15	$98.10
Purchase #5	$116.55	9.591%	$127.7283	$127.73	$127.75	$127.70
Purchase #6	$124.37	4.545%	$130.0226	$130.02	$130.00	$130.00
Purchase #7	$120.44	6.420%	$128.1722	$128.17	$128.15	$128.20
7 purchase totals =	$736.60		$797.9750	$797.98	$797.95	$797.90