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	$72.77	5.166%	$76.5293	$76.53	$76.55	$76.50
Purchase #2	$86.36	5.364%	$90.9924	$90.99	$91.00	$91.00
Purchase #3	$178.59	5.616%	$188.6196	$188.62	$188.60	$188.60
Purchase #4	$39.39	9.389%	$43.0883	$43.09	$43.10	$43.10
Purchase #5	$79.76	3.278%	$82.3745	$82.37	$82.35	$82.40
Purchase #6	$152.61	3.851%	$158.487	$158.49	$158.50	$158.50
Purchase #7	$132.49	11.419%	$147.619	$147.62	$147.60	$147.60
7 purchase totals =	$741.97		$787.7101	$787.71	$787.70	$787.70