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	$235.55	11.153%	$261.8209	$261.82	$261.80	$261.80
Purchase #2	$80.48	5.108%	$84.5909	$84.59	$84.60	$84.60
Purchase #3	$182.35	13.439%	$206.856	$206.86	$206.85	$206.90
Purchase #4	$69.71	12.767%	$78.6099	$78.61	$78.60	$78.60
Purchase #5	$105.94	3.680%	$109.8386	$109.84	$109.85	$109.80
Purchase #6	$98.83	11.453%	$110.149	$110.15	$110.15	$110.10
Purchase #7	$138.69	8.766%	$150.8476	$150.85	$150.85	$150.80
7 purchase totals =	$911.55		$1,002.7129	$1,002.72	$1,002.70	$1,002.60