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	$147.67	3.314%	$152.5638	$152.56	$152.55	$152.60
Purchase #2	$40.75	4.235%	$42.4758	$42.48	$42.50	$42.50
Purchase #3	$133.52	4.389%	$139.3802	$139.38	$139.40	$139.40
Purchase #4	$106.48	3.388%	$110.0875	$110.09	$110.10	$110.10
Purchase #5	$232.27	9.818%	$255.0743	$255.07	$255.05	$255.10
Purchase #6	$124.69	3.255%	$128.7487	$128.75	$128.75	$128.70
Purchase #7	$102.53	12.668%	$115.5185	$115.52	$115.50	$115.50
7 purchase totals =	$887.91		$943.8488	$943.85	$943.85	$943.90