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	$66.81	8.436%	$72.4461	$72.45	$72.45	$72.40
Purchase #2	$161.77	13.420%	$183.4795	$183.48	$183.50	$183.50
Purchase #3	$74.78	6.261%	$79.462	$79.46	$79.45	$79.50
Purchase #4	$222.49	11.188%	$247.3822	$247.38	$247.40	$247.40
Purchase #5	$223.57	13.402%	$253.5329	$253.53	$253.55	$253.50
Purchase #6	$55.99	6.265%	$59.4978	$59.50	$59.50	$59.50
Purchase #7	$91.36	12.214%	$102.5187	$102.52	$102.50	$102.50
7 purchase totals =	$896.77		$998.3192	$998.32	$998.35	$998.30