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	$206.93	7.686%	$222.8346	$222.83	$222.85	$222.80
Purchase #2	$13.48	5.828%	$14.2656	$14.27	$14.25	$14.30
Purchase #3	$45.83	13.518%	$52.0253	$52.03	$52.05	$52.00
Purchase #4	$62.54	6.348%	$66.51	$66.51	$66.50	$66.50
Purchase #5	$59.97	12.805%	$67.6492	$67.65	$67.65	$67.60
Purchase #6	$68.85	12.556%	$77.4948	$77.49	$77.50	$77.50
Purchase #7	$7.62	12.345%	$8.5607	$8.56	$8.55	$8.60
7 purchase totals =	$465.22		$509.3402	$509.34	$509.35	$509.30