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	$102.64	7.514%	$110.3524	$110.35	$110.35	$110.40
Purchase #2	$49.88	11.189%	$55.4611	$55.46	$55.45	$55.50
Purchase #3	$137.94	4.513%	$144.1652	$144.17	$144.15	$144.20
Purchase #4	$238.55	7.530%	$256.5128	$256.51	$256.50	$256.50
Purchase #5	$224.35	11.330%	$249.7689	$249.77	$249.75	$249.80
Purchase #6	$96.63	6.416%	$102.8298	$102.83	$102.85	$102.80
Purchase #7	$204.62	10.151%	$225.391	$225.39	$225.40	$225.40
7 purchase totals =	$1,054.61		$1,144.4812	$1,144.48	$1,144.45	$1,144.60