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	$80.81	13.126%	$91.4171	$91.42	$91.40	$91.40
Purchase #2	$188.61	10.314%	$208.0632	$208.06	$208.05	$208.10
Purchase #3	$13.87	13.292%	$15.7136	$15.71	$15.70	$15.70
Purchase #4	$138.59	10.330%	$152.9063	$152.91	$152.90	$152.90
Purchase #5	$71.75	9.486%	$78.5562	$78.56	$78.55	$78.60
Purchase #6	$163.36	12.552%	$183.8649	$183.86	$183.85	$183.90
Purchase #7	$167.40	10.855%	$185.5713	$185.57	$185.55	$185.60
7 purchase totals =	$824.39		$916.0926	$916.09	$916.00	$916.20