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	$111.75	10.835%	$123.8581	$123.86	$123.85	$123.90
Purchase #2	$125.67	10.465%	$138.8214	$138.82	$138.80	$138.80
Purchase #3	$111.56	13.799%	$126.9542	$126.95	$126.95	$127.00
Purchase #4	$56.44	5.412%	$59.4945	$59.49	$59.50	$59.50
Purchase #5	$113.31	7.141%	$121.4015	$121.40	$121.40	$121.40
Purchase #6	$101.74	4.343%	$106.1586	$106.16	$106.15	$106.20
Purchase #7	$72.54	12.161%	$81.3616	$81.36	$81.35	$81.40
7 purchase totals =	$693.01		$758.0499	$758.04	$758.00	$758.20