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	$145.96	3.425%	$150.9591	$150.96	$150.95	$151.00
Purchase #2	$145.83	6.663%	$155.5467	$155.55	$155.55	$155.50
Purchase #3	$131.73	9.713%	$144.5249	$144.52	$144.50	$144.50
Purchase #4	$113.91	10.227%	$125.5596	$125.56	$125.55	$125.60
Purchase #5	$163.25	5.801%	$172.7201	$172.72	$172.70	$172.70
Purchase #6	$67.42	3.598%	$69.8458	$69.85	$69.85	$69.80
Purchase #7	$239.75	9.641%	$262.8643	$262.86	$262.85	$262.90
7 purchase totals =	$1,007.85		$1,082.0205	$1,082.02	$1,081.95	$1,082.00