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	$233.34	3.553%	$241.6306	$241.63	$241.65	$241.60
Purchase #2	$205.71	10.358%	$227.0174	$227.02	$227.00	$227.00
Purchase #3	$211.77	10.459%	$233.919	$233.92	$233.90	$233.90
Purchase #4	$180.47	6.697%	$192.5561	$192.56	$192.55	$192.60
Purchase #5	$39.35	5.759%	$41.6162	$41.62	$41.60	$41.60
Purchase #6	$245.59	9.128%	$268.0075	$268.01	$268.00	$268.00
Purchase #7	$94.57	9.810%	$103.8473	$103.85	$103.85	$103.80
7 purchase totals =	$1,210.80		$1,308.5941	$1,308.61	$1,308.55	$1,308.50