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	$231.90	11.413%	$258.3667	$258.37	$258.35	$258.40
Purchase #2	$76.85	5.844%	$81.3411	$81.34	$81.35	$81.30
Purchase #3	$55.42	11.190%	$61.6215	$61.62	$61.60	$61.60
Purchase #4	$247.44	8.240%	$267.8291	$267.83	$267.85	$267.80
Purchase #5	$26.27	8.298%	$28.4499	$28.45	$28.45	$28.40
Purchase #6	$134.34	13.334%	$152.2529	$152.25	$152.25	$152.30
Purchase #7	$144.59	11.792%	$161.6401	$161.64	$161.65	$161.60
7 purchase totals =	$916.81		$1,011.5013	$1,011.50	$1,011.50	$1,011.40