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	$238.48	10.518%	$263.5633	$263.56	$263.55	$263.60
Purchase #2	$230.79	11.258%	$256.7723	$256.77	$256.75	$256.80
Purchase #3	$160.63	4.838%	$168.4013	$168.40	$168.40	$168.40
Purchase #4	$249.54	6.443%	$265.6179	$265.62	$265.60	$265.60
Purchase #5	$62.96	13.354%	$71.3677	$71.37	$71.35	$71.40
Purchase #6	$228.36	11.681%	$255.0347	$255.03	$255.05	$255.00
Purchase #7	$158.51	6.462%	$168.7529	$168.75	$168.75	$168.80
7 purchase totals =	$1,329.27		$1,449.5101	$1,449.50	$1,449.45	$1,449.60