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	$75.59	10.750%	$83.7159	$83.72	$83.70	$83.70
Purchase #2	$12.39	11.862%	$13.8597	$13.86	$13.85	$13.90
Purchase #3	$85.48	9.249%	$93.386	$93.39	$93.40	$93.40
Purchase #4	$94.61	10.221%	$104.2801	$104.28	$104.30	$104.30
Purchase #5	$192.49	12.521%	$216.5917	$216.59	$216.60	$216.60
Purchase #6	$107.61	6.814%	$114.9425	$114.94	$114.95	$114.90
Purchase #7	$54.85	13.215%	$62.0984	$62.10	$62.10	$62.10
7 purchase totals =	$623.02		$688.8743	$688.88	$688.90	$688.90