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	$59.82	13.626%	$67.9711	$67.97	$67.95	$68.00
Purchase #2	$78.85	4.803%	$82.6372	$82.64	$82.65	$82.60
Purchase #3	$115.72	6.838%	$123.6329	$123.63	$123.65	$123.60
Purchase #4	$228.25	11.336%	$254.1244	$254.12	$254.10	$254.10
Purchase #5	$46.30	8.139%	$50.0684	$50.07	$50.05	$50.10
Purchase #6	$96.53	9.366%	$105.571	$105.57	$105.55	$105.60
Purchase #7	$247.84	8.116%	$267.9547	$267.95	$267.95	$268.00
7 purchase totals =	$873.31		$951.9597	$951.95	$951.90	$952.00