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	$30.62	7.774%	$33.0004	$33.00	$33.00	$33.00
Purchase #2	$26.95	3.609%	$27.9226	$27.92	$27.90	$27.90
Purchase #3	$227.82	13.516%	$258.6122	$258.61	$258.60	$258.60
Purchase #4	$181.77	13.278%	$205.9054	$205.91	$205.90	$205.90
Purchase #5	$234.39	10.171%	$258.2298	$258.23	$258.25	$258.20
Purchase #6	$250.56	6.849%	$267.7209	$267.72	$267.70	$267.70
Purchase #7	$42.93	12.301%	$48.2108	$48.21	$48.20	$48.20
7 purchase totals =	$995.04		$1,099.6021	$1,099.60	$1,099.55	$1,099.50