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	$116.64	13.765%	$132.6955	$132.70	$132.70	$132.70
Purchase #2	$190.50	4.164%	$198.4324	$198.43	$198.45	$198.40
Purchase #3	$216.60	7.670%	$233.2132	$233.21	$233.20	$233.20
Purchase #4	$102.39	7.218%	$109.7805	$109.78	$109.80	$109.80
Purchase #5	$18.30	12.872%	$20.6556	$20.66	$20.65	$20.70
Purchase #6	$130.39	8.364%	$141.2958	$141.30	$141.30	$141.30
Purchase #7	$90.71	11.805%	$101.4183	$101.42	$101.40	$101.40
7 purchase totals =	$865.53		$937.4913	$937.50	$937.50	$937.50