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	$217.50	6.129%	$230.8306	$230.83	$230.85	$230.80
Purchase #2	$12.69	9.611%	$13.9096	$13.91	$13.90	$13.90
Purchase #3	$169.32	5.575%	$178.7596	$178.76	$178.75	$178.80
Purchase #4	$30.33	9.853%	$33.3184	$33.32	$33.30	$33.30
Purchase #5	$175.80	11.414%	$195.8658	$195.87	$195.85	$195.90
Purchase #6	$41.56	5.583%	$43.8803	$43.88	$43.90	$43.90
Purchase #7	$166.66	4.336%	$173.8864	$173.89	$173.90	$173.90
7 purchase totals =	$813.86		$870.4507	$870.46	$870.45	$870.50