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	$93.89	6.174%	$99.6868	$99.69	$99.70	$99.70
Purchase #2	$12.27	10.128%	$13.5127	$13.51	$13.50	$13.50
Purchase #3	$157.55	6.738%	$168.1657	$168.17	$168.15	$168.20
Purchase #4	$135.62	5.727%	$143.387	$143.39	$143.40	$143.40
Purchase #5	$181.86	5.521%	$191.9005	$191.90	$191.90	$191.90
Purchase #6	$206.60	4.368%	$215.6243	$215.62	$215.60	$215.60
Purchase #7	$97.25	7.442%	$104.4873	$104.49	$104.50	$104.50
7 purchase totals =	$885.04		$936.7643	$936.77	$936.75	$936.80