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	$217.36	8.219%	$235.2248	$235.22	$235.20	$235.20
Purchase #2	$84.43	7.521%	$90.78	$90.78	$90.80	$90.80
Purchase #3	$8.34	9.479%	$9.1305	$9.13	$9.15	$9.10
Purchase #4	$32.55	13.225%	$36.8547	$36.85	$36.85	$36.90
Purchase #5	$172.83	13.798%	$196.6771	$196.68	$196.70	$196.70
Purchase #6	$127.38	12.183%	$142.8987	$142.90	$142.90	$142.90
Purchase #7	$249.27	4.611%	$260.7638	$260.76	$260.75	$260.80
7 purchase totals =	$892.16		$972.3296	$972.32	$972.35	$972.40