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	$48.30	11.144%	$53.6826	$53.68	$53.70	$53.70
Purchase #2	$151.89	7.810%	$163.7526	$163.75	$163.75	$163.80
Purchase #3	$28.83	12.161%	$32.336	$32.34	$32.35	$32.30
Purchase #4	$38.30	11.296%	$42.6264	$42.63	$42.65	$42.60
Purchase #5	$172.69	5.738%	$182.599	$182.60	$182.60	$182.60
Purchase #6	$98.52	11.109%	$109.4646	$109.46	$109.45	$109.50
Purchase #7	$239.26	8.218%	$258.9224	$258.92	$258.90	$258.90
7 purchase totals =	$777.79		$843.3836	$843.38	$843.40	$843.40