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	$180.80	13.245%	$204.747	$204.75	$204.75	$204.70
Purchase #2	$156.81	4.675%	$164.1409	$164.14	$164.15	$164.10
Purchase #3	$141.89	4.314%	$148.0111	$148.01	$148.00	$148.00
Purchase #4	$21.53	13.855%	$24.513	$24.51	$24.50	$24.50
Purchase #5	$215.77	13.710%	$245.3521	$245.35	$245.35	$245.40
Purchase #6	$21.35	5.661%	$22.5586	$22.56	$22.55	$22.60
Purchase #7	$123.89	3.777%	$128.5693	$128.57	$128.55	$128.60
7 purchase totals =	$862.04		$937.8920	$937.89	$937.85	$937.90