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	$134.63	11.791%	$150.5042	$150.50	$150.50	$150.50
Purchase #2	$92.62	6.379%	$98.5282	$98.53	$98.55	$98.50
Purchase #3	$62.32	5.387%	$65.6772	$65.68	$65.70	$65.70
Purchase #4	$139.51	12.479%	$156.9195	$156.92	$156.90	$156.90
Purchase #5	$183.88	8.527%	$199.5594	$199.56	$199.55	$199.60
Purchase #6	$101.97	6.463%	$108.5603	$108.56	$108.55	$108.60
Purchase #7	$155.30	5.851%	$164.3866	$164.39	$164.40	$164.40
7 purchase totals =	$870.23		$944.1354	$944.14	$944.15	$944.20