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	$128.86	10.670%	$142.6094	$142.61	$142.60	$142.60
Purchase #2	$90.32	5.224%	$95.0383	$95.04	$95.05	$95.00
Purchase #3	$199.49	11.237%	$221.9067	$221.91	$221.90	$221.90
Purchase #4	$238.48	4.250%	$248.6154	$248.62	$248.60	$248.60
Purchase #5	$45.36	6.578%	$48.3438	$48.34	$48.35	$48.30
Purchase #6	$135.95	3.332%	$140.4799	$140.48	$140.50	$140.50
Purchase #7	$150.55	10.670%	$166.6137	$166.61	$166.60	$166.60
7 purchase totals =	$989.01		$1,063.6072	$1,063.61	$1,063.60	$1,063.50