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	$102.55	13.794%	$116.6957	$116.70	$116.70	$116.70
Purchase #2	$221.28	9.839%	$243.0517	$243.05	$243.05	$243.10
Purchase #3	$170.33	11.381%	$189.7153	$189.72	$189.70	$189.70
Purchase #4	$175.38	10.589%	$193.951	$193.95	$193.95	$194.00
Purchase #5	$99.97	11.645%	$111.6115	$111.61	$111.60	$111.60
Purchase #6	$114.97	11.698%	$128.4192	$128.42	$128.40	$128.40
Purchase #7	$74.52	12.539%	$83.8641	$83.86	$83.85	$83.90
7 purchase totals =	$959.00		$1,067.3085	$1,067.31	$1,067.25	$1,067.40