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	$207.96	8.151%	$224.9108	$224.91	$224.90	$224.90
Purchase #2	$217.25	12.264%	$243.8935	$243.89	$243.90	$243.90
Purchase #3	$174.34	12.763%	$196.591	$196.59	$196.60	$196.60
Purchase #4	$75.45	13.200%	$85.4094	$85.41	$85.40	$85.40
Purchase #5	$138.91	6.789%	$148.3406	$148.34	$148.35	$148.30
Purchase #6	$26.39	5.373%	$27.8079	$27.81	$27.80	$27.80
Purchase #7	$36.28	8.252%	$39.2738	$39.27	$39.25	$39.30
7 purchase totals =	$876.58		$966.2270	$966.22	$966.20	$966.20