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	$88.44	9.537%	$96.8745	$96.87	$96.85	$96.90
Purchase #2	$38.46	4.783%	$40.2995	$40.30	$40.30	$40.30
Purchase #3	$137.71	4.434%	$143.8161	$143.82	$143.80	$143.80
Purchase #4	$5.79	5.456%	$6.1059	$6.11	$6.10	$6.10
Purchase #5	$82.54	8.168%	$89.2819	$89.28	$89.30	$89.30
Purchase #6	$171.50	8.730%	$186.472	$186.47	$186.45	$186.50
Purchase #7	$92.57	13.182%	$104.7726	$104.77	$104.75	$104.80
7 purchase totals =	$617.01		$667.6225	$667.62	$667.55	$667.70