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	$77.80	7.751%	$83.8303	$83.83	$83.85	$83.80
Purchase #2	$100.93	8.645%	$109.6554	$109.66	$109.65	$109.70
Purchase #3	$181.50	10.605%	$200.7481	$200.75	$200.75	$200.70
Purchase #4	$166.90	3.193%	$172.2291	$172.23	$172.25	$172.20
Purchase #5	$63.37	11.773%	$70.8306	$70.83	$70.85	$70.80
Purchase #6	$67.74	11.196%	$75.3242	$75.32	$75.30	$75.30
Purchase #7	$164.89	6.535%	$175.6656	$175.67	$175.65	$175.70
7 purchase totals =	$823.13		$888.2833	$888.29	$888.30	$888.20