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	$58.40	6.463%	$62.1744	$62.17	$62.15	$62.20
Purchase #2	$54.39	10.132%	$59.9008	$59.90	$59.90	$59.90
Purchase #3	$82.57	8.818%	$89.851	$89.85	$89.85	$89.90
Purchase #4	$57.59	7.614%	$61.9749	$61.97	$61.95	$62.00
Purchase #5	$208.39	12.648%	$234.7472	$234.75	$234.75	$234.70
Purchase #6	$112.49	10.153%	$123.9111	$123.91	$123.90	$123.90
Purchase #7	$42.95	12.311%	$48.2376	$48.24	$48.25	$48.20
7 purchase totals =	$616.78		$680.7970	$680.79	$680.75	$680.80