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	$72.36	13.547%	$82.1626	$82.16	$82.15	$82.20
Purchase #2	$95.32	5.111%	$100.1918	$100.19	$100.20	$100.20
Purchase #3	$69.86	7.104%	$74.8229	$74.82	$74.80	$74.80
Purchase #4	$126.48	4.698%	$132.422	$132.42	$132.40	$132.40
Purchase #5	$94.73	7.727%	$102.0498	$102.05	$102.05	$102.00
Purchase #6	$7.46	7.550%	$8.0232	$8.02	$8.00	$8.00
Purchase #7	$162.28	3.562%	$168.0604	$168.06	$168.05	$168.10
7 purchase totals =	$628.49		$667.7327	$667.72	$667.65	$667.70