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	$130.85	9.168%	$142.8463	$142.85	$142.85	$142.80
Purchase #2	$113.60	8.702%	$123.4855	$123.49	$123.50	$123.50
Purchase #3	$130.51	7.238%	$139.9563	$139.96	$139.95	$140.00
Purchase #4	$118.81	6.588%	$126.6372	$126.64	$126.65	$126.60
Purchase #5	$62.73	13.681%	$71.3121	$71.31	$71.30	$71.30
Purchase #6	$213.33	9.265%	$233.095	$233.10	$233.10	$233.10
Purchase #7	$41.91	6.386%	$44.5864	$44.59	$44.60	$44.60
7 purchase totals =	$811.74		$881.9188	$881.94	$881.95	$881.90