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	$34.30	6.202%	$36.4273	$36.43	$36.45	$36.40
Purchase #2	$107.64	5.178%	$113.2136	$113.21	$113.20	$113.20
Purchase #3	$13.74	5.614%	$14.5114	$14.51	$14.50	$14.50
Purchase #4	$213.79	3.409%	$221.0781	$221.08	$221.10	$221.10
Purchase #5	$35.77	4.324%	$37.3167	$37.32	$37.30	$37.30
Purchase #6	$68.97	5.718%	$72.9137	$72.91	$72.90	$72.90
Purchase #7	$189.59	3.835%	$196.8608	$196.86	$196.85	$196.90
7 purchase totals =	$663.80		$692.3216	$692.32	$692.30	$692.30