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	$232.65	13.873%	$264.9255	$264.93	$264.95	$264.90
Purchase #2	$230.68	11.209%	$256.5369	$256.54	$256.55	$256.50
Purchase #3	$241.56	6.129%	$256.3652	$256.37	$256.35	$256.40
Purchase #4	$68.29	13.701%	$77.6464	$77.65	$77.65	$77.60
Purchase #5	$75.60	4.175%	$78.7563	$78.76	$78.75	$78.80
Purchase #6	$229.82	4.683%	$240.5825	$240.58	$240.60	$240.60
Purchase #7	$66.64	13.314%	$75.5124	$75.51	$75.50	$75.50
7 purchase totals =	$1,145.24		$1,250.3252	$1,250.34	$1,250.35	$1,250.30