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	$53.33	11.472%	$59.448	$59.45	$59.45	$59.40
Purchase #2	$150.61	7.812%	$162.3757	$162.38	$162.40	$162.40
Purchase #3	$22.58	8.454%	$24.4889	$24.49	$24.50	$24.50
Purchase #4	$76.92	10.571%	$85.0512	$85.05	$85.05	$85.10
Purchase #5	$100.39	6.866%	$107.2828	$107.28	$107.30	$107.30
Purchase #6	$46.39	6.846%	$49.5659	$49.57	$49.55	$49.60
Purchase #7	$33.93	7.873%	$36.6013	$36.60	$36.60	$36.60
7 purchase totals =	$484.15		$524.8138	$524.82	$524.85	$524.90