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	$95.75	8.424%	$103.816	$103.82	$103.80	$103.80
Purchase #2	$231.48	4.115%	$241.0054	$241.01	$241.00	$241.00
Purchase #3	$148.88	11.393%	$165.8419	$165.84	$165.85	$165.80
Purchase #4	$57.64	7.405%	$61.9082	$61.91	$61.90	$61.90
Purchase #5	$217.98	7.117%	$233.4936	$233.49	$233.50	$233.50
Purchase #6	$10.91	13.148%	$12.3444	$12.34	$12.35	$12.30
Purchase #7	$18.38	4.828%	$19.2674	$19.27	$19.25	$19.30
7 purchase totals =	$781.02		$837.6769	$837.68	$837.65	$837.60