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	$227.79	8.331%	$246.7672	$246.77	$246.75	$246.80
Purchase #2	$24.30	4.748%	$25.4538	$25.45	$25.45	$25.50
Purchase #3	$71.49	9.423%	$78.2265	$78.23	$78.25	$78.20
Purchase #4	$224.97	13.853%	$256.1351	$256.14	$256.15	$256.10
Purchase #5	$86.75	13.511%	$98.4708	$98.47	$98.45	$98.50
Purchase #6	$60.38	4.110%	$62.8616	$62.86	$62.85	$62.90
Purchase #7	$215.80	8.698%	$234.5703	$234.57	$234.55	$234.60
7 purchase totals =	$911.48		$1,002.4853	$1,002.49	$1,002.45	$1,002.60