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	$70.53	3.242%	$72.8166	$72.82	$72.80	$72.80
Purchase #2	$65.98	10.548%	$72.9396	$72.94	$72.95	$72.90
Purchase #3	$170.34	10.607%	$188.408	$188.41	$188.40	$188.40
Purchase #4	$97.78	5.384%	$103.0445	$103.04	$103.05	$103.00
Purchase #5	$41.85	3.775%	$43.4298	$43.43	$43.45	$43.40
Purchase #6	$232.29	7.112%	$248.8105	$248.81	$248.80	$248.80
Purchase #7	$24.89	10.217%	$27.433	$27.43	$27.45	$27.40
7 purchase totals =	$703.66		$756.8820	$756.88	$756.90	$756.70