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	$119.31	6.783%	$127.4028	$127.40	$127.40	$127.40
Purchase #2	$41.33	7.295%	$44.345	$44.35	$44.35	$44.30
Purchase #3	$176.32	7.305%	$189.2002	$189.20	$189.20	$189.20
Purchase #4	$84.79	6.806%	$90.5608	$90.56	$90.55	$90.60
Purchase #5	$70.89	6.614%	$75.5787	$75.58	$75.60	$75.60
Purchase #6	$70.43	9.655%	$77.23	$77.23	$77.25	$77.20
Purchase #7	$12.67	4.338%	$13.2196	$13.22	$13.20	$13.20
7 purchase totals =	$575.74		$617.5371	$617.54	$617.55	$617.50