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	$57.86	8.606%	$62.8394	$62.84	$62.85	$62.80
Purchase #2	$65.49	11.239%	$72.8504	$72.85	$72.85	$72.90
Purchase #3	$118.53	8.185%	$128.2317	$128.23	$128.25	$128.20
Purchase #4	$40.68	6.113%	$43.1668	$43.17	$43.15	$43.20
Purchase #5	$49.66	6.143%	$52.7106	$52.71	$52.70	$52.70
Purchase #6	$202.52	10.469%	$223.7218	$223.72	$223.70	$223.70
Purchase #7	$220.31	9.579%	$241.4135	$241.41	$241.40	$241.40
7 purchase totals =	$755.05		$824.9342	$824.93	$824.90	$824.90