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	$171.57	4.860%	$179.9083	$179.91	$179.90	$179.90
Purchase #2	$9.68	7.182%	$10.3752	$10.38	$10.40	$10.40
Purchase #3	$137.29	13.782%	$156.2113	$156.21	$156.20	$156.20
Purchase #4	$62.46	5.453%	$65.8659	$65.87	$65.85	$65.90
Purchase #5	$174.98	9.352%	$191.3441	$191.34	$191.35	$191.30
Purchase #6	$190.39	3.231%	$196.5415	$196.54	$196.55	$196.50
Purchase #7	$111.44	7.176%	$119.4369	$119.44	$119.45	$119.40
7 purchase totals =	$857.81		$919.6832	$919.69	$919.70	$919.60