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	$132.94	10.217%	$146.5225	$146.52	$146.50	$146.50
Purchase #2	$173.53	5.396%	$182.8937	$182.89	$182.90	$182.90
Purchase #3	$135.96	8.258%	$147.1876	$147.19	$147.20	$147.20
Purchase #4	$140.25	9.195%	$153.146	$153.15	$153.15	$153.10
Purchase #5	$96.38	7.146%	$103.2673	$103.27	$103.25	$103.30
Purchase #6	$229.34	11.212%	$255.0536	$255.05	$255.05	$255.10
Purchase #7	$141.97	12.772%	$160.1024	$160.10	$160.10	$160.10
7 purchase totals =	$1,050.37		$1,148.1731	$1,148.17	$1,148.15	$1,148.20