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	$86.30	11.709%	$96.4049	$96.40	$96.40	$96.40
Purchase #2	$163.52	4.741%	$171.2725	$171.27	$171.25	$171.30
Purchase #3	$51.68	8.164%	$55.8992	$55.90	$55.90	$55.90
Purchase #4	$172.77	10.427%	$190.7847	$190.78	$190.80	$190.80
Purchase #5	$11.91	9.248%	$13.0114	$13.01	$13.00	$13.00
Purchase #6	$140.71	4.405%	$146.9083	$146.91	$146.90	$146.90
Purchase #7	$69.49	4.716%	$72.7671	$72.77	$72.75	$72.80
7 purchase totals =	$696.38		$747.0481	$747.04	$747.00	$747.10