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	$131.43	9.483%	$143.8935	$143.89	$143.90	$143.90
Purchase #2	$106.54	13.362%	$120.7759	$120.78	$120.80	$120.80
Purchase #3	$62.46	9.183%	$68.1957	$68.20	$68.20	$68.20
Purchase #4	$167.60	11.677%	$187.1707	$187.17	$187.15	$187.20
Purchase #5	$158.94	4.252%	$165.6981	$165.70	$165.70	$165.70
Purchase #6	$77.51	6.728%	$82.7249	$82.72	$82.70	$82.70
Purchase #7	$232.71	9.608%	$255.0688	$255.07	$255.05	$255.10
7 purchase totals =	$937.19		$1,023.5276	$1,023.53	$1,023.50	$1,023.60