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	$205.50	3.765%	$213.2371	$213.24	$213.25	$213.20
Purchase #2	$77.48	6.334%	$82.3876	$82.39	$82.40	$82.40
Purchase #3	$77.78	6.526%	$82.8559	$82.86	$82.85	$82.90
Purchase #4	$95.97	7.799%	$103.4547	$103.45	$103.45	$103.50
Purchase #5	$184.46	10.810%	$204.4001	$204.40	$204.40	$204.40
Purchase #6	$153.89	10.601%	$170.2039	$170.20	$170.20	$170.20
Purchase #7	$81.66	5.631%	$86.2583	$86.26	$86.25	$86.30
7 purchase totals =	$876.74		$942.7976	$942.80	$942.80	$942.90