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	$166.85	5.230%	$175.5763	$175.58	$175.60	$175.60
Purchase #2	$179.68	3.362%	$185.7208	$185.72	$185.70	$185.70
Purchase #3	$101.40	10.518%	$112.0653	$112.07	$112.05	$112.10
Purchase #4	$101.51	7.296%	$108.9162	$108.92	$108.90	$108.90
Purchase #5	$224.36	6.393%	$238.7033	$238.70	$238.70	$238.70
Purchase #6	$63.43	12.524%	$71.374	$71.37	$71.35	$71.40
Purchase #7	$157.72	7.202%	$169.079	$169.08	$169.10	$169.10
7 purchase totals =	$994.95		$1,061.4349	$1,061.44	$1,061.40	$1,061.50