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	$58.93	9.837%	$64.7269	$64.73	$64.75	$64.70
Purchase #2	$211.62	7.406%	$227.2926	$227.29	$227.30	$227.30
Purchase #3	$211.78	4.595%	$221.5113	$221.51	$221.50	$221.50
Purchase #4	$190.35	13.630%	$216.2947	$216.29	$216.30	$216.30
Purchase #5	$95.70	13.333%	$108.4597	$108.46	$108.45	$108.50
Purchase #6	$104.30	5.332%	$109.8613	$109.86	$109.85	$109.90
Purchase #7	$133.54	3.734%	$138.5264	$138.53	$138.55	$138.50
7 purchase totals =	$1,006.22		$1,086.6729	$1,086.67	$1,086.70	$1,086.70