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	$247.81	5.253%	$260.8275	$260.83	$260.85	$260.80
Purchase #2	$33.67	10.831%	$37.3168	$37.32	$37.30	$37.30
Purchase #3	$225.60	6.304%	$239.8218	$239.82	$239.80	$239.80
Purchase #4	$136.39	5.529%	$143.931	$143.93	$143.95	$143.90
Purchase #5	$214.31	4.816%	$224.6312	$224.63	$224.65	$224.60
Purchase #6	$51.92	12.224%	$58.2667	$58.27	$58.25	$58.30
Purchase #7	$96.34	5.472%	$101.6117	$101.61	$101.60	$101.60
7 purchase totals =	$1,006.04		$1,066.4067	$1,066.41	$1,066.40	$1,066.30