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	$210.69	10.476%	$232.7619	$232.76	$232.75	$232.80
Purchase #2	$155.89	13.195%	$176.4597	$176.46	$176.45	$176.50
Purchase #3	$58.97	9.286%	$64.446	$64.45	$64.45	$64.40
Purchase #4	$134.89	4.196%	$140.55	$140.55	$140.55	$140.60
Purchase #5	$250.76	5.245%	$263.9124	$263.91	$263.90	$263.90
Purchase #6	$98.38	10.599%	$108.8073	$108.81	$108.80	$108.80
Purchase #7	$144.98	5.456%	$152.8901	$152.89	$152.90	$152.90
7 purchase totals =	$1,054.56		$1,139.8274	$1,139.83	$1,139.80	$1,139.90