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	$38.50	13.667%	$43.7618	$43.76	$43.75	$43.80
Purchase #2	$224.76	8.794%	$244.5254	$244.53	$244.55	$244.50
Purchase #3	$22.95	10.555%	$25.3724	$25.37	$25.35	$25.40
Purchase #4	$180.89	10.293%	$199.509	$199.51	$199.50	$199.50
Purchase #5	$201.52	5.646%	$212.8978	$212.90	$212.90	$212.90
Purchase #6	$130.96	13.526%	$148.6736	$148.67	$148.65	$148.70
Purchase #7	$127.76	10.574%	$141.2693	$141.27	$141.25	$141.30
7 purchase totals =	$927.34		$1,016.0093	$1,016.01	$1,015.95	$1,016.10