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	$228.53	7.308%	$245.231	$245.23	$245.25	$245.20
Purchase #2	$38.72	12.593%	$43.596	$43.60	$43.60	$43.60
Purchase #3	$129.70	7.836%	$139.8633	$139.86	$139.85	$139.90
Purchase #4	$198.91	5.298%	$209.4483	$209.45	$209.45	$209.40
Purchase #5	$17.80	12.457%	$20.0173	$20.02	$20.00	$20.00
Purchase #6	$155.68	4.560%	$162.779	$162.78	$162.80	$162.80
Purchase #7	$181.74	10.210%	$200.2957	$200.30	$200.30	$200.30
7 purchase totals =	$951.08		$1,021.2306	$1,021.24	$1,021.25	$1,021.20