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	$162.29	3.555%	$168.0594	$168.06	$168.05	$168.10
Purchase #2	$77.33	7.162%	$82.8684	$82.87	$82.85	$82.90
Purchase #3	$79.87	12.728%	$90.0359	$90.04	$90.05	$90.00
Purchase #4	$18.82	9.268%	$20.5642	$20.56	$20.55	$20.60
Purchase #5	$142.57	7.750%	$153.6192	$153.62	$153.60	$153.60
Purchase #6	$220.87	9.531%	$241.9211	$241.92	$241.90	$241.90
Purchase #7	$167.61	6.735%	$178.8985	$178.90	$178.90	$178.90
7 purchase totals =	$869.36		$935.9667	$935.97	$935.90	$936.00