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	$138.47	8.851%	$150.726	$150.73	$150.75	$150.70
Purchase #2	$227.73	9.722%	$249.8699	$249.87	$249.85	$249.90
Purchase #3	$152.52	3.831%	$158.363	$158.36	$158.35	$158.40
Purchase #4	$172.93	9.516%	$189.386	$189.39	$189.40	$189.40
Purchase #5	$177.58	4.698%	$185.9227	$185.92	$185.90	$185.90
Purchase #6	$217.27	3.589%	$225.0678	$225.07	$225.05	$225.10
Purchase #7	$60.39	3.462%	$62.4807	$62.48	$62.50	$62.50
7 purchase totals =	$1,146.89		$1,221.8161	$1,221.82	$1,221.80	$1,221.90