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	$82.29	12.684%	$92.7277	$92.73	$92.75	$92.70
Purchase #2	$119.63	8.720%	$130.0617	$130.06	$130.05	$130.10
Purchase #3	$217.85	4.587%	$227.8428	$227.84	$227.85	$227.80
Purchase #4	$113.60	8.514%	$123.2719	$123.27	$123.25	$123.30
Purchase #5	$94.45	11.290%	$105.1134	$105.11	$105.10	$105.10
Purchase #6	$28.37	5.305%	$29.875	$29.88	$29.90	$29.90
Purchase #7	$227.42	12.819%	$256.573	$256.57	$256.55	$256.60
7 purchase totals =	$883.61		$965.4655	$965.46	$965.45	$965.50