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	$103.97	8.430%	$112.7347	$112.73	$112.75	$112.70
Purchase #2	$115.64	6.624%	$123.3	$123.30	$123.30	$123.30
Purchase #3	$201.60	10.271%	$222.3063	$222.31	$222.30	$222.30
Purchase #4	$190.42	4.724%	$199.4154	$199.42	$199.40	$199.40
Purchase #5	$224.47	8.463%	$243.4669	$243.47	$243.45	$243.50
Purchase #6	$141.44	6.454%	$150.5685	$150.57	$150.55	$150.60
Purchase #7	$28.35	9.119%	$30.9352	$30.94	$30.95	$30.90
7 purchase totals =	$1,005.89		$1,082.7270	$1,082.74	$1,082.70	$1,082.70