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	$200.30	7.688%	$215.6991	$215.70	$215.70	$215.70
Purchase #2	$85.46	4.144%	$89.0015	$89.00	$89.00	$89.00
Purchase #3	$36.60	8.501%	$39.7114	$39.71	$39.70	$39.70
Purchase #4	$27.68	13.671%	$31.4641	$31.46	$31.45	$31.50
Purchase #5	$235.38	10.347%	$259.7348	$259.73	$259.75	$259.70
Purchase #6	$109.50	8.833%	$119.1721	$119.17	$119.15	$119.20
Purchase #7	$189.54	11.265%	$210.8917	$210.89	$210.90	$210.90
7 purchase totals =	$884.46		$965.6747	$965.66	$965.65	$965.70