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	$233.81	7.506%	$251.3598	$251.36	$251.35	$251.40
Purchase #2	$104.81	4.376%	$109.3965	$109.40	$109.40	$109.40
Purchase #3	$36.75	9.850%	$40.3699	$40.37	$40.35	$40.40
Purchase #4	$73.47	4.636%	$76.8761	$76.88	$76.90	$76.90
Purchase #5	$172.89	4.102%	$179.9819	$179.98	$180.00	$180.00
Purchase #6	$237.40	11.657%	$265.0737	$265.07	$265.05	$265.10
Purchase #7	$95.91	10.264%	$105.7542	$105.75	$105.75	$105.80
7 purchase totals =	$955.04		$1,028.8121	$1,028.81	$1,028.80	$1,029.00