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	$95.70	3.513%	$99.0619	$99.06	$99.05	$99.10
Purchase #2	$44.60	11.674%	$49.8066	$49.81	$49.80	$49.80
Purchase #3	$34.57	12.441%	$38.8709	$38.87	$38.85	$38.90
Purchase #4	$83.96	12.712%	$94.633	$94.63	$94.65	$94.60
Purchase #5	$95.34	8.688%	$103.6231	$103.62	$103.60	$103.60
Purchase #6	$148.35	13.199%	$167.9307	$167.93	$167.95	$167.90
Purchase #7	$146.95	12.613%	$165.4848	$165.48	$165.50	$165.50
7 purchase totals =	$649.47		$719.4110	$719.40	$719.40	$719.40