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	$132.78	12.202%	$148.9818	$148.98	$149.00	$149.00
Purchase #2	$198.27	12.199%	$222.457	$222.46	$222.45	$222.50
Purchase #3	$42.28	6.492%	$45.0248	$45.02	$45.00	$45.00
Purchase #4	$125.34	6.845%	$133.9195	$133.92	$133.90	$133.90
Purchase #5	$157.39	13.379%	$178.4472	$178.45	$178.45	$178.40
Purchase #6	$120.69	5.792%	$127.6804	$127.68	$127.70	$127.70
Purchase #7	$196.56	5.721%	$207.8052	$207.81	$207.80	$207.80
7 purchase totals =	$973.31		$1,064.3159	$1,064.32	$1,064.30	$1,064.30