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	$107.28	6.300%	$114.0386	$114.04	$114.05	$114.00
Purchase #2	$85.83	7.773%	$92.5016	$92.50	$92.50	$92.50
Purchase #3	$73.59	4.835%	$77.1481	$77.15	$77.15	$77.10
Purchase #4	$35.40	8.794%	$38.5131	$38.51	$38.50	$38.50
Purchase #5	$92.96	9.248%	$101.5569	$101.56	$101.55	$101.60
Purchase #6	$87.64	13.196%	$99.205	$99.21	$99.20	$99.20
Purchase #7	$132.53	6.376%	$140.9801	$140.98	$141.00	$141.00
7 purchase totals =	$615.23		$663.9434	$663.95	$663.95	$663.90