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	$241.71	8.809%	$263.0022	$263.00	$263.00	$263.00
Purchase #2	$43.86	12.746%	$49.4504	$49.45	$49.45	$49.50
Purchase #3	$50.97	8.848%	$55.4798	$55.48	$55.50	$55.50
Purchase #4	$95.68	8.306%	$103.6272	$103.63	$103.65	$103.60
Purchase #5	$62.37	8.668%	$67.7762	$67.78	$67.80	$67.80
Purchase #6	$51.31	3.496%	$53.1038	$53.10	$53.10	$53.10
Purchase #7	$180.98	6.307%	$192.3944	$192.39	$192.40	$192.40
7 purchase totals =	$726.88		$784.8340	$784.83	$784.90	$784.90