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	$85.74	9.599%	$93.9702	$93.97	$93.95	$94.00
Purchase #2	$45.87	13.559%	$52.0895	$52.09	$52.10	$52.10
Purchase #3	$20.96	3.400%	$21.6726	$21.67	$21.65	$21.70
Purchase #4	$119.79	3.627%	$124.1348	$124.13	$124.15	$124.10
Purchase #5	$179.34	9.419%	$196.232	$196.23	$196.25	$196.20
Purchase #6	$37.52	13.674%	$42.6505	$42.65	$42.65	$42.70
Purchase #7	$122.45	10.102%	$134.8199	$134.82	$134.80	$134.80
7 purchase totals =	$611.67		$665.5695	$665.56	$665.55	$665.60