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	$130.85	9.252%	$142.9562	$142.96	$142.95	$143.00
Purchase #2	$196.91	11.460%	$219.4759	$219.48	$219.50	$219.50
Purchase #3	$108.54	6.731%	$115.8458	$115.85	$115.85	$115.80
Purchase #4	$194.53	5.792%	$205.7972	$205.80	$205.80	$205.80
Purchase #5	$145.43	4.163%	$151.4843	$151.48	$151.50	$151.50
Purchase #6	$48.89	9.432%	$53.5013	$53.50	$53.50	$53.50
Purchase #7	$75.69	3.771%	$78.5443	$78.54	$78.55	$78.50
7 purchase totals =	$900.84		$967.6050	$967.61	$967.65	$967.60