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	$49.30	12.256%	$55.3422	$55.34	$55.35	$55.30
Purchase #2	$184.78	4.236%	$192.6073	$192.61	$192.60	$192.60
Purchase #3	$145.45	13.119%	$164.5316	$164.53	$164.55	$164.50
Purchase #4	$213.89	6.512%	$227.8185	$227.82	$227.80	$227.80
Purchase #5	$226.32	3.508%	$234.2593	$234.26	$234.25	$234.30
Purchase #6	$10.47	8.160%	$11.3244	$11.32	$11.30	$11.30
Purchase #7	$166.61	10.617%	$184.299	$184.30	$184.30	$184.30
7 purchase totals =	$996.82		$1,070.1823	$1,070.18	$1,070.15	$1,070.10