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	$86.77	4.586%	$90.7493	$90.75	$90.75	$90.70
Purchase #2	$190.86	9.748%	$209.465	$209.47	$209.45	$209.50
Purchase #3	$148.79	9.531%	$162.9712	$162.97	$162.95	$163.00
Purchase #4	$31.40	5.419%	$33.1016	$33.10	$33.10	$33.10
Purchase #5	$14.90	8.465%	$16.1613	$16.16	$16.15	$16.20
Purchase #6	$111.89	10.210%	$123.314	$123.31	$123.30	$123.30
Purchase #7	$136.49	8.782%	$148.4766	$148.48	$148.50	$148.50
7 purchase totals =	$721.10		$784.2390	$784.24	$784.20	$784.30