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	$55.93	5.852%	$59.203	$59.20	$59.20	$59.20
Purchase #2	$78.36	10.844%	$86.8574	$86.86	$86.85	$86.90
Purchase #3	$176.64	10.820%	$195.7524	$195.75	$195.75	$195.80
Purchase #4	$150.84	12.408%	$169.5562	$169.56	$169.55	$169.60
Purchase #5	$99.81	4.168%	$103.9701	$103.97	$103.95	$104.00
Purchase #6	$52.60	13.496%	$59.6989	$59.70	$59.70	$59.70
Purchase #7	$183.86	4.373%	$191.9002	$191.90	$191.90	$191.90
7 purchase totals =	$798.04		$866.9382	$866.94	$866.90	$867.10