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	$135.44	5.176%	$142.4504	$142.45	$142.45	$142.50
Purchase #2	$179.39	10.702%	$198.5883	$198.59	$198.60	$198.60
Purchase #3	$167.89	10.422%	$185.3875	$185.39	$185.40	$185.40
Purchase #4	$219.40	8.723%	$238.5383	$238.54	$238.55	$238.50
Purchase #5	$184.35	8.204%	$199.4741	$199.47	$199.45	$199.50
Purchase #6	$57.43	11.430%	$63.9942	$63.99	$64.00	$64.00
Purchase #7	$155.69	7.659%	$167.6143	$167.61	$167.60	$167.60
7 purchase totals =	$1,099.59		$1,196.0471	$1,196.04	$1,196.05	$1,196.10