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	$75.87	10.232%	$83.633	$83.63	$83.65	$83.60
Purchase #2	$205.97	6.676%	$219.7206	$219.72	$219.70	$219.70
Purchase #3	$96.92	6.391%	$103.1142	$103.11	$103.10	$103.10
Purchase #4	$83.92	8.184%	$90.788	$90.79	$90.80	$90.80
Purchase #5	$69.48	11.623%	$77.5557	$77.56	$77.55	$77.60
Purchase #6	$248.89	7.105%	$266.5736	$266.57	$266.55	$266.60
Purchase #7	$204.67	10.858%	$226.8931	$226.89	$226.90	$226.90
7 purchase totals =	$985.72		$1,068.2782	$1,068.27	$1,068.25	$1,068.30