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	$22.32	11.342%	$24.8515	$24.85	$24.85	$24.90
Purchase #2	$70.73	4.453%	$73.8796	$73.88	$73.90	$73.90
Purchase #3	$207.55	3.410%	$214.6275	$214.63	$214.65	$214.60
Purchase #4	$53.78	11.351%	$59.8846	$59.88	$59.90	$59.90
Purchase #5	$66.77	8.735%	$72.6024	$72.60	$72.60	$72.60
Purchase #6	$71.68	8.254%	$77.5965	$77.60	$77.60	$77.60
Purchase #7	$50.38	13.813%	$57.339	$57.34	$57.35	$57.30
7 purchase totals =	$543.21		$580.7811	$580.78	$580.85	$580.80