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	$95.46	6.788%	$101.9398	$101.94	$101.95	$101.90
Purchase #2	$159.58	3.571%	$165.2786	$165.28	$165.30	$165.30
Purchase #3	$105.72	6.153%	$112.225	$112.23	$112.25	$112.20
Purchase #4	$213.92	9.107%	$233.4017	$233.40	$233.40	$233.40
Purchase #5	$148.45	5.182%	$156.1427	$156.14	$156.15	$156.10
Purchase #6	$133.35	9.338%	$145.8022	$145.80	$145.80	$145.80
Purchase #7	$191.77	12.492%	$215.7259	$215.73	$215.75	$215.70
7 purchase totals =	$1,048.25		$1,130.5159	$1,130.52	$1,130.60	$1,130.40