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	$192.44	7.288%	$206.465	$206.47	$206.45	$206.50
Purchase #2	$175.89	12.618%	$198.0838	$198.08	$198.10	$198.10
Purchase #3	$218.89	13.268%	$247.9323	$247.93	$247.95	$247.90
Purchase #4	$167.35	3.121%	$172.573	$172.57	$172.55	$172.60
Purchase #5	$117.75	7.835%	$126.9757	$126.98	$127.00	$127.00
Purchase #6	$130.48	3.141%	$134.5784	$134.58	$134.60	$134.60
Purchase #7	$210.62	5.482%	$222.1662	$222.17	$222.15	$222.20
7 purchase totals =	$1,213.42		$1,308.7744	$1,308.78	$1,308.80	$1,308.90