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	$137.61	4.202%	$143.3924	$143.39	$143.40	$143.40
Purchase #2	$140.56	8.628%	$152.6875	$152.69	$152.70	$152.70
Purchase #3	$76.98	4.639%	$80.5511	$80.55	$80.55	$80.60
Purchase #4	$214.95	6.657%	$229.2592	$229.26	$229.25	$229.30
Purchase #5	$211.72	4.738%	$221.7513	$221.75	$221.75	$221.80
Purchase #6	$10.38	10.815%	$11.5026	$11.50	$11.50	$11.50
Purchase #7	$76.46	8.448%	$82.9193	$82.92	$82.90	$82.90
7 purchase totals =	$868.66		$922.0634	$922.06	$922.05	$922.20