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	$59.66	13.855%	$67.9259	$67.93	$67.95	$67.90
Purchase #2	$185.56	7.783%	$200.0021	$200.00	$200.00	$200.00
Purchase #3	$219.72	10.185%	$242.0985	$242.10	$242.10	$242.10
Purchase #4	$7.88	3.152%	$8.1284	$8.13	$8.15	$8.10
Purchase #5	$94.86	7.621%	$102.0893	$102.09	$102.10	$102.10
Purchase #6	$198.76	6.393%	$211.4667	$211.47	$211.45	$211.50
Purchase #7	$34.33	7.144%	$36.7825	$36.78	$36.80	$36.80
7 purchase totals =	$800.77		$868.4934	$868.50	$868.55	$868.50