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	$175.38	9.756%	$192.4901	$192.49	$192.50	$192.50
Purchase #2	$170.40	11.186%	$189.4609	$189.46	$189.45	$189.50
Purchase #3	$52.62	7.355%	$56.4902	$56.49	$56.50	$56.50
Purchase #4	$117.51	9.512%	$128.6876	$128.69	$128.70	$128.70
Purchase #5	$75.93	3.540%	$78.6179	$78.62	$78.60	$78.60
Purchase #6	$176.71	3.358%	$182.6439	$182.64	$182.65	$182.60
Purchase #7	$216.82	13.677%	$246.4745	$246.47	$246.45	$246.50
7 purchase totals =	$985.37		$1,074.8651	$1,074.86	$1,074.85	$1,074.90