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	$226.39	5.760%	$239.4301	$239.43	$239.45	$239.40
Purchase #2	$90.88	10.754%	$100.6532	$100.65	$100.65	$100.70
Purchase #3	$191.33	11.322%	$212.9924	$212.99	$213.00	$213.00
Purchase #4	$7.41	6.285%	$7.8757	$7.88	$7.90	$7.90
Purchase #5	$178.96	11.125%	$198.8693	$198.87	$198.85	$198.90
Purchase #6	$194.71	13.249%	$220.5071	$220.51	$220.50	$220.50
Purchase #7	$92.79	13.846%	$105.6377	$105.64	$105.65	$105.60
7 purchase totals =	$982.47		$1,085.9655	$1,085.97	$1,086.00	$1,086.00