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	$153.96	9.292%	$168.266	$168.27	$168.25	$168.30
Purchase #2	$27.81	8.216%	$30.0949	$30.09	$30.10	$30.10
Purchase #3	$101.69	6.366%	$108.1636	$108.16	$108.15	$108.20
Purchase #4	$125.58	5.314%	$132.2533	$132.25	$132.25	$132.30
Purchase #5	$49.30	4.219%	$51.38	$51.38	$51.40	$51.40
Purchase #6	$131.46	7.586%	$141.4326	$141.43	$141.45	$141.40
Purchase #7	$66.38	9.831%	$72.9058	$72.91	$72.90	$72.90
7 purchase totals =	$656.18		$704.4962	$704.49	$704.50	$704.60