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	$205.37	8.568%	$222.9661	$222.97	$222.95	$223.00
Purchase #2	$185.49	11.201%	$206.2667	$206.27	$206.25	$206.30
Purchase #3	$160.37	8.156%	$173.4498	$173.45	$173.45	$173.40
Purchase #4	$49.61	5.405%	$52.2914	$52.29	$52.30	$52.30
Purchase #5	$20.94	4.609%	$21.9051	$21.91	$21.90	$21.90
Purchase #6	$96.79	3.797%	$100.4651	$100.47	$100.45	$100.50
Purchase #7	$131.25	9.711%	$143.9957	$144.00	$144.00	$144.00
7 purchase totals =	$849.82		$921.3399	$921.36	$921.30	$921.40