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	$145.62	4.704%	$152.47	$152.47	$152.45	$152.50
Purchase #2	$20.54	12.293%	$23.065	$23.07	$23.05	$23.10
Purchase #3	$89.61	3.572%	$92.8109	$92.81	$92.80	$92.80
Purchase #4	$19.57	4.782%	$20.5058	$20.51	$20.50	$20.50
Purchase #5	$11.96	10.467%	$13.2119	$13.21	$13.20	$13.20
Purchase #6	$170.72	6.215%	$181.3302	$181.33	$181.35	$181.30
Purchase #7	$142.50	8.388%	$154.4529	$154.45	$154.45	$154.50
7 purchase totals =	$600.52		$637.8467	$637.85	$637.80	$637.90