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	$143.33	7.814%	$154.5298	$154.53	$154.55	$154.50
Purchase #2	$231.28	3.793%	$240.0525	$240.05	$240.05	$240.10
Purchase #3	$183.31	3.499%	$189.724	$189.72	$189.70	$189.70
Purchase #4	$246.67	13.840%	$280.8091	$280.81	$280.80	$280.80
Purchase #5	$100.58	5.233%	$105.8434	$105.84	$105.85	$105.80
Purchase #6	$40.86	6.598%	$43.5559	$43.56	$43.55	$43.60
Purchase #7	$65.85	7.536%	$70.8125	$70.81	$70.80	$70.80
7 purchase totals =	$1,011.88		$1,085.3272	$1,085.32	$1,085.30	$1,085.30