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	$61.87	9.379%	$67.6728	$67.67	$67.65	$67.70
Purchase #2	$245.95	4.421%	$256.8234	$256.82	$256.80	$256.80
Purchase #3	$58.68	9.729%	$64.389	$64.39	$64.40	$64.40
Purchase #4	$99.55	10.141%	$109.6454	$109.65	$109.65	$109.60
Purchase #5	$72.48	5.343%	$76.3526	$76.35	$76.35	$76.40
Purchase #6	$100.30	9.290%	$109.6179	$109.62	$109.60	$109.60
Purchase #7	$103.84	4.493%	$108.5055	$108.51	$108.50	$108.50
7 purchase totals =	$742.67		$793.0066	$793.01	$792.95	$793.00