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	$61.83	5.510%	$65.2368	$65.24	$65.25	$65.20
Purchase #2	$59.48	4.133%	$61.9383	$61.94	$61.95	$61.90
Purchase #3	$73.41	11.190%	$81.6246	$81.62	$81.60	$81.60
Purchase #4	$113.77	5.427%	$119.9443	$119.94	$119.95	$119.90
Purchase #5	$186.89	12.239%	$209.7635	$209.76	$209.75	$209.80
Purchase #6	$60.88	13.714%	$69.2291	$69.23	$69.25	$69.20
Purchase #7	$139.64	9.680%	$153.1572	$153.16	$153.15	$153.20
7 purchase totals =	$695.90		$760.8938	$760.89	$760.90	$760.80