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	$67.82	6.395%	$72.1571	$72.16	$72.15	$72.20
Purchase #2	$224.65	5.556%	$237.1316	$237.13	$237.15	$237.10
Purchase #3	$35.59	9.478%	$38.9632	$38.96	$38.95	$39.00
Purchase #4	$21.77	9.801%	$23.9037	$23.90	$23.90	$23.90
Purchase #5	$100.84	10.720%	$111.65	$111.65	$111.65	$111.70
Purchase #6	$249.43	10.407%	$275.3882	$275.39	$275.40	$275.40
Purchase #7	$161.95	7.626%	$174.3003	$174.30	$174.30	$174.30
7 purchase totals =	$862.05		$933.4941	$933.49	$933.50	$933.60