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	$25.70	5.603%	$27.14	$27.14	$27.15	$27.10
Purchase #2	$56.30	10.872%	$62.4209	$62.42	$62.40	$62.40
Purchase #3	$196.42	8.347%	$212.8152	$212.82	$212.80	$212.80
Purchase #4	$176.47	6.808%	$188.4841	$188.48	$188.50	$188.50
Purchase #5	$128.29	11.699%	$143.2986	$143.30	$143.30	$143.30
Purchase #6	$246.68	13.531%	$280.0583	$280.06	$280.05	$280.10
Purchase #7	$134.71	11.846%	$150.6677	$150.67	$150.65	$150.70
7 purchase totals =	$964.57		$1,064.8848	$1,064.89	$1,064.85	$1,064.90