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	$191.34	11.608%	$213.5507	$213.55	$213.55	$213.60
Purchase #2	$159.50	12.273%	$179.0754	$179.08	$179.10	$179.10
Purchase #3	$186.33	5.249%	$196.1105	$196.11	$196.10	$196.10
Purchase #4	$125.71	11.736%	$140.4633	$140.46	$140.45	$140.50
Purchase #5	$172.94	6.735%	$184.5875	$184.59	$184.60	$184.60
Purchase #6	$60.66	8.193%	$65.6299	$65.63	$65.65	$65.60
Purchase #7	$152.84	5.585%	$161.3761	$161.38	$161.40	$161.40
7 purchase totals =	$1,049.32		$1,140.7934	$1,140.80	$1,140.85	$1,140.90