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	$91.76	12.627%	$103.3465	$103.35	$103.35	$103.30
Purchase #2	$187.56	4.671%	$196.3209	$196.32	$196.30	$196.30
Purchase #3	$123.43	7.384%	$132.5441	$132.54	$132.55	$132.50
Purchase #4	$88.28	4.402%	$92.1661	$92.17	$92.15	$92.20
Purchase #5	$134.59	12.491%	$151.4016	$151.40	$151.40	$151.40
Purchase #6	$56.77	6.605%	$60.5197	$60.52	$60.50	$60.50
Purchase #7	$191.97	5.405%	$202.346	$202.35	$202.35	$202.30
7 purchase totals =	$874.36		$938.6449	$938.65	$938.60	$938.50