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	$192.57	9.476%	$210.8179	$210.82	$210.80	$210.80
Purchase #2	$109.63	13.654%	$124.5989	$124.60	$124.60	$124.60
Purchase #3	$86.55	4.551%	$90.4889	$90.49	$90.50	$90.50
Purchase #4	$229.98	5.341%	$242.2632	$242.26	$242.25	$242.30
Purchase #5	$39.92	11.642%	$44.5675	$44.57	$44.55	$44.60
Purchase #6	$32.69	3.667%	$33.8887	$33.89	$33.90	$33.90
Purchase #7	$123.95	10.147%	$136.5272	$136.53	$136.55	$136.50
7 purchase totals =	$815.29		$883.1523	$883.16	$883.15	$883.20