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	$105.70	10.620%	$116.9253	$116.93	$116.95	$116.90
Purchase #2	$205.30	12.733%	$231.4408	$231.44	$231.45	$231.40
Purchase #3	$117.85	12.244%	$132.2796	$132.28	$132.30	$132.30
Purchase #4	$145.38	10.199%	$160.2073	$160.21	$160.20	$160.20
Purchase #5	$183.62	3.256%	$189.5987	$189.60	$189.60	$189.60
Purchase #6	$33.40	11.599%	$37.2741	$37.27	$37.25	$37.30
Purchase #7	$150.77	13.263%	$170.7666	$170.77	$170.75	$170.80
7 purchase totals =	$942.02		$1,038.4924	$1,038.50	$1,038.50	$1,038.50