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	$94.31	10.115%	$103.8495	$103.85	$103.85	$103.80
Purchase #2	$44.89	3.248%	$46.348	$46.35	$46.35	$46.30
Purchase #3	$193.88	6.471%	$206.426	$206.43	$206.45	$206.40
Purchase #4	$247.71	5.506%	$261.3489	$261.35	$261.35	$261.30
Purchase #5	$24.31	5.335%	$25.6069	$25.61	$25.60	$25.60
Purchase #6	$116.25	13.353%	$131.7729	$131.77	$131.75	$131.80
Purchase #7	$18.55	12.494%	$20.8676	$20.87	$20.85	$20.90
7 purchase totals =	$739.90		$796.2198	$796.23	$796.20	$796.10