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	$250.89	5.205%	$263.9488	$263.95	$263.95	$263.90
Purchase #2	$131.64	4.419%	$137.4572	$137.46	$137.45	$137.50
Purchase #3	$52.97	12.556%	$59.6209	$59.62	$59.60	$59.60
Purchase #4	$185.62	5.233%	$195.3335	$195.33	$195.35	$195.30
Purchase #5	$41.68	10.678%	$46.1306	$46.13	$46.15	$46.10
Purchase #6	$133.95	7.718%	$144.2883	$144.29	$144.30	$144.30
Purchase #7	$47.96	7.584%	$51.5973	$51.60	$51.60	$51.60
7 purchase totals =	$844.71		$898.3766	$898.38	$898.40	$898.30