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	$77.95	12.371%	$87.5932	$87.59	$87.60	$87.60
Purchase #2	$28.52	3.793%	$29.6018	$29.60	$29.60	$29.60
Purchase #3	$98.83	9.352%	$108.0726	$108.07	$108.05	$108.10
Purchase #4	$157.25	7.227%	$168.6145	$168.61	$168.60	$168.60
Purchase #5	$70.83	10.210%	$78.0617	$78.06	$78.05	$78.10
Purchase #6	$216.26	4.373%	$225.717	$225.72	$225.70	$225.70
Purchase #7	$24.31	6.173%	$25.8107	$25.81	$25.80	$25.80
7 purchase totals =	$673.95		$723.4715	$723.46	$723.40	$723.50