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	$219.38	10.838%	$243.1564	$243.16	$243.15	$243.20
Purchase #2	$97.38	12.642%	$109.6908	$109.69	$109.70	$109.70
Purchase #3	$49.45	13.167%	$55.9611	$55.96	$55.95	$56.00
Purchase #4	$164.68	11.492%	$183.605	$183.61	$183.60	$183.60
Purchase #5	$240.35	10.233%	$264.945	$264.95	$264.95	$264.90
Purchase #6	$166.50	8.507%	$180.6642	$180.66	$180.65	$180.70
Purchase #7	$17.93	10.773%	$19.8616	$19.86	$19.85	$19.90
7 purchase totals =	$955.67		$1,057.8841	$1,057.89	$1,057.85	$1,058.00