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	$194.88	5.140%	$204.8968	$204.90	$204.90	$204.90
Purchase #2	$97.48	7.119%	$104.4196	$104.42	$104.40	$104.40
Purchase #3	$62.91	4.874%	$65.9762	$65.98	$66.00	$66.00
Purchase #4	$141.72	13.530%	$160.8947	$160.89	$160.90	$160.90
Purchase #5	$83.89	6.162%	$89.0593	$89.06	$89.05	$89.10
Purchase #6	$33.59	11.545%	$37.468	$37.47	$37.45	$37.50
Purchase #7	$54.75	4.601%	$57.269	$57.27	$57.25	$57.30
7 purchase totals =	$669.22		$719.9836	$719.99	$719.95	$720.10