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	$92.69	12.834%	$104.5858	$104.59	$104.60	$104.60
Purchase #2	$120.27	9.603%	$131.8195	$131.82	$131.80	$131.80
Purchase #3	$27.92	12.536%	$31.4201	$31.42	$31.40	$31.40
Purchase #4	$238.80	9.196%	$260.76	$260.76	$260.75	$260.80
Purchase #5	$91.44	9.683%	$100.2941	$100.29	$100.30	$100.30
Purchase #6	$50.69	13.589%	$57.5783	$57.58	$57.60	$57.60
Purchase #7	$153.77	4.765%	$161.0971	$161.10	$161.10	$161.10
7 purchase totals =	$775.58		$847.5549	$847.56	$847.55	$847.60