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	$202.85	5.703%	$214.4185	$214.42	$214.40	$214.40
Purchase #2	$51.93	7.612%	$55.8829	$55.88	$55.90	$55.90
Purchase #3	$29.43	9.189%	$32.1343	$32.13	$32.15	$32.10
Purchase #4	$219.70	8.380%	$238.1109	$238.11	$238.10	$238.10
Purchase #5	$24.82	9.354%	$27.1417	$27.14	$27.15	$27.10
Purchase #6	$205.32	11.464%	$228.8579	$228.86	$228.85	$228.90
Purchase #7	$227.74	13.869%	$259.3253	$259.33	$259.35	$259.30
7 purchase totals =	$961.79		$1,055.8715	$1,055.87	$1,055.90	$1,055.80