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	$225.36	3.650%	$233.5856	$233.59	$233.60	$233.60
Purchase #2	$56.88	4.602%	$59.4976	$59.50	$59.50	$59.50
Purchase #3	$159.88	7.866%	$172.4562	$172.46	$172.45	$172.50
Purchase #4	$233.45	7.470%	$250.8887	$250.89	$250.90	$250.90
Purchase #5	$206.93	5.226%	$217.7442	$217.74	$217.75	$217.70
Purchase #6	$178.89	4.378%	$186.7218	$186.72	$186.70	$186.70
Purchase #7	$173.42	7.442%	$186.3259	$186.33	$186.35	$186.30
7 purchase totals =	$1,234.81		$1,307.2200	$1,307.23	$1,307.25	$1,307.20