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	$223.26	4.584%	$233.4942	$233.49	$233.50	$233.50
Purchase #2	$11.70	12.217%	$13.1294	$13.13	$13.15	$13.10
Purchase #3	$116.32	9.501%	$127.3716	$127.37	$127.35	$127.40
Purchase #4	$52.30	5.200%	$55.0196	$55.02	$55.00	$55.00
Purchase #5	$108.31	11.818%	$121.1101	$121.11	$121.10	$121.10
Purchase #6	$162.62	10.509%	$179.7097	$179.71	$179.70	$179.70
Purchase #7	$140.44	3.768%	$145.7318	$145.73	$145.75	$145.70
7 purchase totals =	$814.95		$875.5664	$875.56	$875.55	$875.50