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	$78.38	10.493%	$86.6044	$86.60	$86.60	$86.60
Purchase #2	$64.43	4.207%	$67.1406	$67.14	$67.15	$67.10
Purchase #3	$145.39	5.528%	$153.4272	$153.43	$153.45	$153.40
Purchase #4	$96.83	3.834%	$100.5425	$100.54	$100.55	$100.50
Purchase #5	$146.44	10.545%	$161.8821	$161.88	$161.90	$161.90
Purchase #6	$126.57	6.747%	$135.1097	$135.11	$135.10	$135.10
Purchase #7	$58.73	4.249%	$61.2254	$61.23	$61.25	$61.20
7 purchase totals =	$716.77		$765.9319	$765.93	$766.00	$765.80