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	$165.27	10.602%	$182.7919	$182.79	$182.80	$182.80
Purchase #2	$248.53	9.660%	$272.538	$272.54	$272.55	$272.50
Purchase #3	$75.41	13.267%	$85.4146	$85.41	$85.40	$85.40
Purchase #4	$86.71	11.210%	$96.4302	$96.43	$96.45	$96.40
Purchase #5	$126.66	6.335%	$134.6839	$134.68	$134.70	$134.70
Purchase #6	$82.43	9.661%	$90.3936	$90.39	$90.40	$90.40
Purchase #7	$168.81	8.805%	$183.6737	$183.67	$183.65	$183.70
7 purchase totals =	$953.82		$1,045.9259	$1,045.91	$1,045.95	$1,045.90