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	$10.76	7.864%	$11.6062	$11.61	$11.60	$11.60
Purchase #2	$67.83	5.213%	$71.366	$71.37	$71.35	$71.40
Purchase #3	$114.55	4.716%	$119.9522	$119.95	$119.95	$120.00
Purchase #4	$73.75	3.532%	$76.3549	$76.35	$76.35	$76.40
Purchase #5	$93.86	13.266%	$106.3115	$106.31	$106.30	$106.30
Purchase #6	$68.74	5.498%	$72.5193	$72.52	$72.50	$72.50
Purchase #7	$100.69	9.748%	$110.5053	$110.51	$110.50	$110.50
7 purchase totals =	$530.18		$568.6154	$568.62	$568.55	$568.70