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	$94.54	11.761%	$105.6588	$105.66	$105.65	$105.70
Purchase #2	$58.86	11.405%	$65.573	$65.57	$65.55	$65.60
Purchase #3	$69.83	4.720%	$73.126	$73.13	$73.15	$73.10
Purchase #4	$51.89	7.533%	$55.7989	$55.80	$55.80	$55.80
Purchase #5	$52.82	10.737%	$58.4913	$58.49	$58.50	$58.50
Purchase #6	$113.39	5.659%	$119.8067	$119.81	$119.80	$119.80
Purchase #7	$100.83	8.666%	$109.5679	$109.57	$109.55	$109.60
7 purchase totals =	$542.16		$588.0226	$588.03	$588.00	$588.10