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	$146.64	9.778%	$160.9785	$160.98	$161.00	$161.00
Purchase #2	$193.57	12.340%	$217.4565	$217.46	$217.45	$217.50
Purchase #3	$74.91	4.159%	$78.0255	$78.03	$78.05	$78.00
Purchase #4	$142.61	12.358%	$160.2337	$160.23	$160.25	$160.20
Purchase #5	$200.98	11.122%	$223.333	$223.33	$223.35	$223.30
Purchase #6	$175.94	11.848%	$196.7854	$196.79	$196.80	$196.80
Purchase #7	$99.54	7.553%	$107.0583	$107.06	$107.05	$107.10
7 purchase totals =	$1,034.19		$1,143.8709	$1,143.88	$1,143.95	$1,143.90