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	$205.68	3.332%	$212.5333	$212.53	$212.55	$212.50
Purchase #2	$57.35	12.810%	$64.6965	$64.70	$64.70	$64.70
Purchase #3	$72.88	6.471%	$77.5961	$77.60	$77.60	$77.60
Purchase #4	$42.81	6.160%	$45.4471	$45.45	$45.45	$45.40
Purchase #5	$94.83	10.722%	$104.9977	$105.00	$105.00	$105.00
Purchase #6	$81.38	5.632%	$85.9633	$85.96	$85.95	$86.00
Purchase #7	$172.83	9.871%	$189.89	$189.89	$189.90	$189.90
7 purchase totals =	$727.76		$781.1240	$781.13	$781.15	$781.10