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	$139.40	9.872%	$153.1616	$153.16	$153.15	$153.20
Purchase #2	$58.57	10.112%	$64.4926	$64.49	$64.50	$64.50
Purchase #3	$95.51	5.167%	$100.445	$100.45	$100.45	$100.40
Purchase #4	$139.86	5.221%	$147.1621	$147.16	$147.15	$147.20
Purchase #5	$234.60	10.433%	$259.0758	$259.08	$259.10	$259.10
Purchase #6	$69.85	4.412%	$72.9318	$72.93	$72.95	$72.90
Purchase #7	$86.91	10.118%	$95.7036	$95.70	$95.70	$95.70
7 purchase totals =	$824.70		$892.9725	$892.97	$893.00	$893.00