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	$206.85	3.409%	$213.9015	$213.90	$213.90	$213.90
Purchase #2	$148.62	13.407%	$168.5455	$168.55	$168.55	$168.50
Purchase #3	$158.39	6.686%	$168.98	$168.98	$169.00	$169.00
Purchase #4	$249.82	13.418%	$283.3408	$283.34	$283.35	$283.30
Purchase #5	$95.86	13.843%	$109.1299	$109.13	$109.15	$109.10
Purchase #6	$94.25	9.811%	$103.4969	$103.50	$103.50	$103.50
Purchase #7	$52.82	12.153%	$59.2392	$59.24	$59.25	$59.20
7 purchase totals =	$1,006.61		$1,106.6338	$1,106.64	$1,106.70	$1,106.50