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	$169.61	11.136%	$188.4978	$188.50	$188.50	$188.50
Purchase #2	$38.38	4.299%	$40.03	$40.03	$40.05	$40.00
Purchase #3	$128.58	9.826%	$141.2143	$141.21	$141.20	$141.20
Purchase #4	$225.26	13.449%	$255.5552	$255.56	$255.55	$255.60
Purchase #5	$208.92	6.662%	$222.8383	$222.84	$222.85	$222.80
Purchase #6	$169.59	9.412%	$185.5518	$185.55	$185.55	$185.60
Purchase #7	$9.93	10.503%	$10.9729	$10.97	$10.95	$11.00
7 purchase totals =	$950.27		$1,044.6603	$1,044.66	$1,044.65	$1,044.70