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	$235.99	5.382%	$248.691	$248.69	$248.70	$248.70
Purchase #2	$84.82	5.716%	$89.6683	$89.67	$89.65	$89.70
Purchase #3	$193.78	13.857%	$220.6321	$220.63	$220.65	$220.60
Purchase #4	$139.61	11.347%	$155.4515	$155.45	$155.45	$155.50
Purchase #5	$104.58	9.500%	$114.5151	$114.52	$114.50	$114.50
Purchase #6	$65.30	9.354%	$71.4082	$71.41	$71.40	$71.40
Purchase #7	$159.51	13.359%	$180.8189	$180.82	$180.80	$180.80
7 purchase totals =	$983.59		$1,081.1851	$1,081.19	$1,081.15	$1,081.20