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	$188.30	10.157%	$207.4256	$207.43	$207.45	$207.40
Purchase #2	$211.92	13.522%	$240.5758	$240.58	$240.60	$240.60
Purchase #3	$181.36	8.382%	$196.5616	$196.56	$196.55	$196.60
Purchase #4	$65.56	10.410%	$72.3848	$72.38	$72.40	$72.40
Purchase #5	$34.85	3.498%	$36.0691	$36.07	$36.05	$36.10
Purchase #6	$112.49	13.207%	$127.3466	$127.35	$127.35	$127.30
Purchase #7	$118.53	6.259%	$125.9488	$125.95	$125.95	$125.90
7 purchase totals =	$913.01		$1,006.3123	$1,006.32	$1,006.35	$1,006.30