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	$152.48	11.367%	$169.8124	$169.81	$169.80	$169.80
Purchase #2	$192.89	3.219%	$199.0991	$199.10	$199.10	$199.10
Purchase #3	$39.79	4.487%	$41.5754	$41.58	$41.60	$41.60
Purchase #4	$40.36	9.785%	$44.3092	$44.31	$44.30	$44.30
Purchase #5	$89.82	11.535%	$100.1807	$100.18	$100.20	$100.20
Purchase #6	$108.47	7.499%	$116.6042	$116.60	$116.60	$116.60
Purchase #7	$219.56	5.659%	$231.9849	$231.98	$232.00	$232.00
7 purchase totals =	$843.37		$903.5659	$903.56	$903.60	$903.60