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	$185.32	8.217%	$200.5477	$200.55	$200.55	$200.50
Purchase #2	$147.41	5.382%	$155.3436	$155.34	$155.35	$155.30
Purchase #3	$167.46	8.141%	$181.0929	$181.09	$181.10	$181.10
Purchase #4	$173.29	9.821%	$190.3088	$190.31	$190.30	$190.30
Purchase #5	$81.66	13.704%	$92.8507	$92.85	$92.85	$92.90
Purchase #6	$162.43	10.217%	$179.0255	$179.03	$179.05	$179.00
Purchase #7	$226.29	3.188%	$233.5041	$233.50	$233.50	$233.50
7 purchase totals =	$1,143.86		$1,232.6733	$1,232.67	$1,232.70	$1,232.60