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	$46.82	10.724%	$51.841	$51.84	$51.85	$51.80
Purchase #2	$103.59	5.609%	$109.4004	$109.40	$109.40	$109.40
Purchase #3	$199.88	10.688%	$221.2432	$221.24	$221.25	$221.20
Purchase #4	$98.95	12.264%	$111.0852	$111.09	$111.10	$111.10
Purchase #5	$141.64	10.535%	$156.5618	$156.56	$156.55	$156.60
Purchase #6	$124.47	13.588%	$141.383	$141.38	$141.40	$141.40
Purchase #7	$205.28	12.802%	$231.5599	$231.56	$231.55	$231.60
7 purchase totals =	$920.63		$1,023.0745	$1,023.07	$1,023.10	$1,023.10