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	$50.52	4.162%	$52.6226	$52.62	$52.60	$52.60
Purchase #2	$98.31	5.681%	$103.895	$103.90	$103.90	$103.90
Purchase #3	$241.69	13.149%	$273.4698	$273.47	$273.45	$273.50
Purchase #4	$72.50	9.280%	$79.228	$79.23	$79.25	$79.20
Purchase #5	$38.94	12.473%	$43.797	$43.80	$43.80	$43.80
Purchase #6	$41.50	12.731%	$46.7834	$46.78	$46.80	$46.80
Purchase #7	$150.62	12.323%	$169.1809	$169.18	$169.20	$169.20
7 purchase totals =	$694.08		$768.9767	$768.98	$769.00	$769.00