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	$234.39	11.255%	$260.7706	$260.77	$260.75	$260.80
Purchase #2	$13.56	6.846%	$14.4883	$14.49	$14.50	$14.50
Purchase #3	$39.78	12.331%	$44.6853	$44.69	$44.70	$44.70
Purchase #4	$98.75	4.578%	$103.2708	$103.27	$103.25	$103.30
Purchase #5	$82.95	8.231%	$89.7776	$89.78	$89.80	$89.80
Purchase #6	$27.68	8.181%	$29.9445	$29.94	$29.95	$29.90
Purchase #7	$140.71	12.247%	$157.9428	$157.94	$157.95	$157.90
7 purchase totals =	$637.82		$700.8799	$700.88	$700.90	$700.90