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	$128.68	11.257%	$143.1655	$143.17	$143.15	$143.20
Purchase #2	$25.90	11.578%	$28.8987	$28.90	$28.90	$28.90
Purchase #3	$139.81	3.338%	$144.4769	$144.48	$144.50	$144.50
Purchase #4	$86.81	6.559%	$92.5039	$92.50	$92.50	$92.50
Purchase #5	$130.58	8.148%	$141.2197	$141.22	$141.20	$141.20
Purchase #6	$81.85	5.704%	$86.5187	$86.52	$86.50	$86.50
Purchase #7	$114.35	5.670%	$120.8336	$120.83	$120.85	$120.80
7 purchase totals =	$707.98		$757.6170	$757.62	$757.60	$757.60