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	$249.44	7.215%	$267.4371	$267.44	$267.45	$267.40
Purchase #2	$37.32	5.230%	$39.2718	$39.27	$39.25	$39.30
Purchase #3	$124.89	5.327%	$131.5429	$131.54	$131.55	$131.50
Purchase #4	$39.56	11.341%	$44.0465	$44.05	$44.05	$44.00
Purchase #5	$184.32	3.103%	$190.0394	$190.04	$190.05	$190.00
Purchase #6	$103.96	10.525%	$114.9018	$114.90	$114.90	$114.90
Purchase #7	$82.85	3.583%	$85.8185	$85.82	$85.80	$85.80
7 purchase totals =	$822.34		$873.0580	$873.06	$873.05	$872.90