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	$90.34	5.571%	$95.3728	$95.37	$95.35	$95.40
Purchase #2	$103.93	9.156%	$113.4458	$113.45	$113.45	$113.40
Purchase #3	$70.69	11.798%	$79.03	$79.03	$79.05	$79.00
Purchase #4	$61.59	8.372%	$66.7463	$66.75	$66.75	$66.70
Purchase #5	$196.47	12.670%	$221.3627	$221.36	$221.35	$221.40
Purchase #6	$245.63	7.594%	$264.2831	$264.28	$264.30	$264.30
Purchase #7	$72.62	7.627%	$78.1587	$78.16	$78.15	$78.20
7 purchase totals =	$841.27		$918.3994	$918.40	$918.40	$918.40