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	$89.55	6.587%	$95.4487	$95.45	$95.45	$95.40
Purchase #2	$91.94	7.787%	$99.0994	$99.10	$99.10	$99.10
Purchase #3	$54.89	7.791%	$59.1665	$59.17	$59.15	$59.20
Purchase #4	$135.45	6.214%	$143.8669	$143.87	$143.85	$143.90
Purchase #5	$78.39	9.351%	$85.7202	$85.72	$85.70	$85.70
Purchase #6	$136.75	5.343%	$144.0566	$144.06	$144.05	$144.10
Purchase #7	$153.45	12.412%	$172.4962	$172.50	$172.50	$172.50
7 purchase totals =	$740.42		$799.8545	$799.87	$799.80	$799.90