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	$100.32	5.279%	$105.6159	$105.62	$105.60	$105.60
Purchase #2	$174.29	12.603%	$196.2558	$196.26	$196.25	$196.30
Purchase #3	$51.34	7.109%	$54.9898	$54.99	$55.00	$55.00
Purchase #4	$24.93	3.343%	$25.7634	$25.76	$25.75	$25.80
Purchase #5	$168.67	5.800%	$178.4529	$178.45	$178.45	$178.50
Purchase #6	$24.73	3.468%	$25.5876	$25.59	$25.60	$25.60
Purchase #7	$103.73	11.352%	$115.5054	$115.51	$115.50	$115.50
7 purchase totals =	$648.01		$702.1708	$702.18	$702.15	$702.30