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	$88.98	7.367%	$95.5352	$95.54	$95.55	$95.50
Purchase #2	$127.43	13.754%	$144.9567	$144.96	$144.95	$145.00
Purchase #3	$89.47	8.543%	$97.1134	$97.11	$97.10	$97.10
Purchase #4	$44.67	9.243%	$48.7988	$48.80	$48.80	$48.80
Purchase #5	$209.66	11.365%	$233.4879	$233.49	$233.50	$233.50
Purchase #6	$148.90	4.402%	$155.4546	$155.45	$155.45	$155.50
Purchase #7	$78.73	13.783%	$89.5814	$89.58	$89.60	$89.60
7 purchase totals =	$787.84		$864.9280	$864.93	$864.95	$865.00