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	$96.74	3.456%	$100.0833	$100.08	$100.10	$100.10
Purchase #2	$178.73	9.640%	$195.9596	$195.96	$195.95	$196.00
Purchase #3	$152.70	10.770%	$169.1458	$169.15	$169.15	$169.10
Purchase #4	$32.51	5.364%	$34.2538	$34.25	$34.25	$34.30
Purchase #5	$100.95	4.455%	$105.4473	$105.45	$105.45	$105.40
Purchase #6	$212.89	12.492%	$239.4842	$239.48	$239.50	$239.50
Purchase #7	$33.37	7.749%	$35.9558	$35.96	$35.95	$36.00
7 purchase totals =	$807.89		$880.3298	$880.33	$880.35	$880.40