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	$100.32	3.733%	$104.0649	$104.06	$104.05	$104.10
Purchase #2	$173.70	3.586%	$179.9289	$179.93	$179.95	$179.90
Purchase #3	$69.46	11.326%	$77.327	$77.33	$77.35	$77.30
Purchase #4	$86.57	10.286%	$95.4746	$95.47	$95.45	$95.50
Purchase #5	$249.50	8.478%	$270.6526	$270.65	$270.65	$270.70
Purchase #6	$70.85	10.782%	$78.489	$78.49	$78.50	$78.50
Purchase #7	$231.45	8.697%	$251.5792	$251.58	$251.60	$251.60
7 purchase totals =	$981.85		$1,057.5162	$1,057.51	$1,057.55	$1,057.60