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	$175.64	13.822%	$199.917	$199.92	$199.90	$199.90
Purchase #2	$139.88	11.156%	$155.485	$155.49	$155.50	$155.50
Purchase #3	$40.70	8.678%	$44.2319	$44.23	$44.25	$44.20
Purchase #4	$74.26	5.271%	$78.1742	$78.17	$78.15	$78.20
Purchase #5	$234.27	13.333%	$265.5052	$265.51	$265.50	$265.50
Purchase #6	$149.35	4.322%	$155.8049	$155.80	$155.80	$155.80
Purchase #7	$154.45	7.529%	$166.0785	$166.08	$166.10	$166.10
7 purchase totals =	$968.55		$1,065.1967	$1,065.20	$1,065.20	$1,065.20