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	$74.34	5.768%	$78.6279	$78.63	$78.65	$78.60
Purchase #2	$139.34	10.567%	$154.0641	$154.06	$154.05	$154.10
Purchase #3	$231.59	11.277%	$257.7064	$257.71	$257.70	$257.70
Purchase #4	$248.84	5.396%	$262.2674	$262.27	$262.25	$262.30
Purchase #5	$93.27	10.546%	$103.1063	$103.11	$103.10	$103.10
Purchase #6	$76.41	7.837%	$82.3983	$82.40	$82.40	$82.40
Purchase #7	$100.63	8.693%	$109.3778	$109.38	$109.40	$109.40
7 purchase totals =	$964.42		$1,047.5482	$1,047.56	$1,047.55	$1,047.60