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	$13.92	3.618%	$14.4236	$14.42	$14.40	$14.40
Purchase #2	$74.89	4.770%	$78.4623	$78.46	$78.45	$78.50
Purchase #3	$240.63	10.764%	$266.5314	$266.53	$266.55	$266.50
Purchase #4	$9.91	5.696%	$10.4745	$10.47	$10.45	$10.50
Purchase #5	$204.33	9.613%	$223.9722	$223.97	$223.95	$224.00
Purchase #6	$232.57	7.759%	$250.6151	$250.62	$250.60	$250.60
Purchase #7	$200.51	13.541%	$227.6611	$227.66	$227.65	$227.70
7 purchase totals =	$976.76		$1,072.1402	$1,072.13	$1,072.05	$1,072.20