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	$41.33	10.129%	$45.5163	$45.52	$45.50	$45.50
Purchase #2	$229.83	5.833%	$243.236	$243.24	$243.25	$243.20
Purchase #3	$11.72	4.630%	$12.2626	$12.26	$12.25	$12.30
Purchase #4	$78.91	9.536%	$86.4349	$86.43	$86.45	$86.40
Purchase #5	$14.80	4.515%	$15.4682	$15.47	$15.45	$15.50
Purchase #6	$248.42	10.772%	$275.1798	$275.18	$275.20	$275.20
Purchase #7	$140.86	5.516%	$148.6298	$148.63	$148.65	$148.60
7 purchase totals =	$765.87		$826.7276	$826.73	$826.75	$826.70