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	$232.66	9.404%	$254.5393	$254.54	$254.55	$254.50
Purchase #2	$221.61	9.625%	$242.94	$242.94	$242.95	$242.90
Purchase #3	$100.96	13.621%	$114.7118	$114.71	$114.70	$114.70
Purchase #4	$49.95	10.327%	$55.1083	$55.11	$55.10	$55.10
Purchase #5	$69.46	12.699%	$78.2807	$78.28	$78.30	$78.30
Purchase #6	$120.43	3.486%	$124.6282	$124.63	$124.65	$124.60
Purchase #7	$103.52	12.546%	$116.5076	$116.51	$116.50	$116.50
7 purchase totals =	$898.59		$986.7159	$986.72	$986.75	$986.60