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	$210.33	4.760%	$220.3417	$220.34	$220.35	$220.30
Purchase #2	$83.68	10.410%	$92.3911	$92.39	$92.40	$92.40
Purchase #3	$46.27	11.388%	$51.5392	$51.54	$51.55	$51.50
Purchase #4	$58.64	11.285%	$65.2575	$65.26	$65.25	$65.30
Purchase #5	$235.63	8.623%	$255.9484	$255.95	$255.95	$255.90
Purchase #6	$165.96	11.172%	$184.5011	$184.50	$184.50	$184.50
Purchase #7	$31.28	3.709%	$32.4402	$32.44	$32.45	$32.40
7 purchase totals =	$831.79		$902.4192	$902.42	$902.45	$902.30