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	$166.41	3.568%	$172.3475	$172.35	$172.35	$172.30
Purchase #2	$136.74	12.405%	$153.7026	$153.70	$153.70	$153.70
Purchase #3	$55.47	12.562%	$62.4381	$62.44	$62.45	$62.40
Purchase #4	$109.51	9.402%	$119.8061	$119.81	$119.80	$119.80
Purchase #5	$55.56	7.753%	$59.8676	$59.87	$59.85	$59.90
Purchase #6	$245.56	5.750%	$259.6797	$259.68	$259.70	$259.70
Purchase #7	$246.25	12.114%	$276.0807	$276.08	$276.10	$276.10
7 purchase totals =	$1,015.50		$1,103.9223	$1,103.93	$1,103.95	$1,103.90