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	$93.27	7.449%	$100.2177	$100.22	$100.20	$100.20
Purchase #2	$167.88	10.673%	$185.7978	$185.80	$185.80	$185.80
Purchase #3	$181.96	3.780%	$188.8381	$188.84	$188.85	$188.80
Purchase #4	$176.37	13.733%	$200.5909	$200.59	$200.60	$200.60
Purchase #5	$23.40	6.123%	$24.8328	$24.83	$24.85	$24.80
Purchase #6	$28.38	3.836%	$29.4687	$29.47	$29.45	$29.50
Purchase #7	$52.35	4.692%	$54.8063	$54.81	$54.80	$54.80
7 purchase totals =	$723.61		$784.5523	$784.56	$784.55	$784.50