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	$205.78	8.285%	$222.8289	$222.83	$222.85	$222.80
Purchase #2	$194.39	9.718%	$213.2808	$213.28	$213.30	$213.30
Purchase #3	$20.65	13.715%	$23.4821	$23.48	$23.50	$23.50
Purchase #4	$150.81	9.856%	$165.6738	$165.67	$165.65	$165.70
Purchase #5	$98.88	4.868%	$103.6935	$103.69	$103.70	$103.70
Purchase #6	$102.56	13.571%	$116.4784	$116.48	$116.50	$116.50
Purchase #7	$36.72	13.838%	$41.8013	$41.80	$41.80	$41.80
7 purchase totals =	$809.79		$887.2388	$887.23	$887.30	$887.30