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	$155.43	3.536%	$160.926	$160.93	$160.95	$160.90
Purchase #2	$207.86	6.615%	$221.6099	$221.61	$221.60	$221.60
Purchase #3	$136.56	3.479%	$141.3109	$141.31	$141.30	$141.30
Purchase #4	$154.82	8.604%	$168.1407	$168.14	$168.15	$168.10
Purchase #5	$215.40	4.807%	$225.7543	$225.75	$225.75	$225.80
Purchase #6	$53.57	3.527%	$55.4594	$55.46	$55.45	$55.50
Purchase #7	$216.37	3.373%	$223.6682	$223.67	$223.65	$223.70
7 purchase totals =	$1,140.01		$1,196.8694	$1,196.87	$1,196.85	$1,196.90