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	$63.25	5.292%	$66.5972	$66.60	$66.60	$66.60
Purchase #2	$52.67	7.299%	$56.5144	$56.51	$56.50	$56.50
Purchase #3	$26.74	8.356%	$28.9744	$28.97	$28.95	$29.00
Purchase #4	$203.63	5.828%	$215.4976	$215.50	$215.50	$215.50
Purchase #5	$213.34	4.204%	$222.3088	$222.31	$222.30	$222.30
Purchase #6	$64.40	12.600%	$72.5144	$72.51	$72.50	$72.50
Purchase #7	$169.33	9.703%	$185.7601	$185.76	$185.75	$185.80
7 purchase totals =	$793.36		$848.1669	$848.16	$848.10	$848.20