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	$193.88	13.342%	$219.7475	$219.75	$219.75	$219.70
Purchase #2	$218.75	3.478%	$226.3581	$226.36	$226.35	$226.40
Purchase #3	$35.82	13.407%	$40.6224	$40.62	$40.60	$40.60
Purchase #4	$49.28	10.389%	$54.3997	$54.40	$54.40	$54.40
Purchase #5	$232.62	13.224%	$263.3817	$263.38	$263.40	$263.40
Purchase #6	$174.35	12.730%	$196.5448	$196.54	$196.55	$196.50
Purchase #7	$121.44	8.260%	$131.4709	$131.47	$131.45	$131.50
7 purchase totals =	$1,026.14		$1,132.5251	$1,132.52	$1,132.50	$1,132.50