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	$195.43	6.749%	$208.6196	$208.62	$208.60	$208.60
Purchase #2	$136.96	11.641%	$152.9035	$152.90	$152.90	$152.90
Purchase #3	$220.74	9.222%	$241.0966	$241.10	$241.10	$241.10
Purchase #4	$164.92	4.496%	$172.3348	$172.33	$172.35	$172.30
Purchase #5	$49.38	3.737%	$51.2253	$51.23	$51.25	$51.20
Purchase #6	$116.41	10.248%	$128.3397	$128.34	$128.35	$128.30
Purchase #7	$124.81	10.249%	$137.6018	$137.60	$137.60	$137.60
7 purchase totals =	$1,008.65		$1,092.1213	$1,092.12	$1,092.15	$1,092.00