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	$237.83	8.689%	$258.495	$258.50	$258.50	$258.50
Purchase #2	$10.71	10.398%	$11.8236	$11.82	$11.80	$11.80
Purchase #3	$213.43	13.465%	$242.1683	$242.17	$242.15	$242.20
Purchase #4	$49.39	12.635%	$55.6304	$55.63	$55.65	$55.60
Purchase #5	$202.66	13.727%	$230.4791	$230.48	$230.50	$230.50
Purchase #6	$162.82	7.771%	$175.4727	$175.47	$175.45	$175.50
Purchase #7	$86.47	3.360%	$89.3754	$89.38	$89.40	$89.40
7 purchase totals =	$963.31		$1,063.4445	$1,063.45	$1,063.45	$1,063.50