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	$174.81	6.140%	$185.5433	$185.54	$185.55	$185.50
Purchase #2	$140.46	3.324%	$145.1289	$145.13	$145.15	$145.10
Purchase #3	$62.34	4.861%	$65.3703	$65.37	$65.35	$65.40
Purchase #4	$51.61	4.730%	$54.0512	$54.05	$54.05	$54.10
Purchase #5	$174.46	13.827%	$198.5826	$198.58	$198.60	$198.60
Purchase #6	$22.64	11.655%	$25.2787	$25.28	$25.30	$25.30
Purchase #7	$23.96	9.672%	$26.2774	$26.28	$26.30	$26.30
7 purchase totals =	$650.28		$700.2324	$700.23	$700.30	$700.30