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	$41.68	5.244%	$43.8657	$43.87	$43.85	$43.90
Purchase #2	$99.61	9.526%	$109.0988	$109.10	$109.10	$109.10
Purchase #3	$183.77	3.163%	$189.5826	$189.58	$189.60	$189.60
Purchase #4	$239.47	12.587%	$269.6121	$269.61	$269.60	$269.60
Purchase #5	$137.64	4.543%	$143.893	$143.89	$143.90	$143.90
Purchase #6	$92.50	11.317%	$102.9682	$102.97	$102.95	$103.00
Purchase #7	$182.59	3.674%	$189.2984	$189.30	$189.30	$189.30
7 purchase totals =	$977.26		$1,048.3188	$1,048.32	$1,048.30	$1,048.40