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	$100.54	5.150%	$105.7178	$105.72	$105.70	$105.70
Purchase #2	$66.69	10.324%	$73.5751	$73.58	$73.60	$73.60
Purchase #3	$24.34	4.269%	$25.3791	$25.38	$25.40	$25.40
Purchase #4	$134.36	13.352%	$152.2997	$152.30	$152.30	$152.30
Purchase #5	$54.58	9.119%	$59.5572	$59.56	$59.55	$59.60
Purchase #6	$12.29	13.230%	$13.916	$13.92	$13.90	$13.90
Purchase #7	$144.58	9.329%	$158.0679	$158.07	$158.05	$158.10
7 purchase totals =	$537.38		$588.5128	$588.53	$588.50	$588.60