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	$112.30	3.757%	$116.5191	$116.52	$116.50	$116.50
Purchase #2	$178.40	6.396%	$189.8105	$189.81	$189.80	$189.80
Purchase #3	$87.66	10.513%	$96.8757	$96.88	$96.90	$96.90
Purchase #4	$144.48	9.395%	$158.0539	$158.05	$158.05	$158.10
Purchase #5	$141.41	3.277%	$146.044	$146.04	$146.05	$146.00
Purchase #6	$174.56	3.663%	$180.9541	$180.95	$180.95	$181.00
Purchase #7	$246.76	4.102%	$256.8821	$256.88	$256.90	$256.90
7 purchase totals =	$1,085.57		$1,145.1394	$1,145.13	$1,145.15	$1,145.20