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	$109.25	6.401%	$116.2431	$116.24	$116.25	$116.20
Purchase #2	$153.86	12.681%	$173.371	$173.37	$173.35	$173.40
Purchase #3	$19.42	10.544%	$21.4676	$21.47	$21.45	$21.50
Purchase #4	$53.44	10.445%	$59.0218	$59.02	$59.00	$59.00
Purchase #5	$150.64	9.189%	$164.4823	$164.48	$164.50	$164.50
Purchase #6	$51.64	6.416%	$54.9532	$54.95	$54.95	$55.00
Purchase #7	$148.64	4.741%	$155.687	$155.69	$155.70	$155.70
7 purchase totals =	$686.89		$745.2260	$745.22	$745.20	$745.30