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	$21.94	3.549%	$22.7187	$22.72	$22.70	$22.70
Purchase #2	$45.76	12.210%	$51.3473	$51.35	$51.35	$51.30
Purchase #3	$130.66	4.273%	$136.2431	$136.24	$136.25	$136.20
Purchase #4	$76.85	12.642%	$86.5654	$86.57	$86.55	$86.60
Purchase #5	$166.88	11.207%	$185.5822	$185.58	$185.60	$185.60
Purchase #6	$172.94	5.501%	$182.4534	$182.45	$182.45	$182.50
Purchase #7	$35.51	6.145%	$37.6921	$37.69	$37.70	$37.70
7 purchase totals =	$650.54		$702.6022	$702.60	$702.60	$702.60