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	$60.42	6.362%	$64.2639	$64.26	$64.25	$64.30
Purchase #2	$109.45	13.618%	$124.3549	$124.35	$124.35	$124.40
Purchase #3	$41.59	12.709%	$46.8757	$46.88	$46.90	$46.90
Purchase #4	$234.99	13.561%	$266.857	$266.86	$266.85	$266.90
Purchase #5	$105.89	3.625%	$109.7285	$109.73	$109.75	$109.70
Purchase #6	$94.44	5.377%	$99.518	$99.52	$99.50	$99.50
Purchase #7	$71.72	6.172%	$76.1466	$76.15	$76.15	$76.10
7 purchase totals =	$718.50		$787.7446	$787.75	$787.75	$787.80