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	$227.33	5.587%	$240.0309	$240.03	$240.05	$240.00
Purchase #2	$231.40	6.196%	$245.7375	$245.74	$245.75	$245.70
Purchase #3	$89.72	6.318%	$95.3885	$95.39	$95.40	$95.40
Purchase #4	$136.71	3.699%	$141.7669	$141.77	$141.75	$141.80
Purchase #5	$89.75	12.176%	$100.678	$100.68	$100.70	$100.70
Purchase #6	$46.79	12.541%	$52.6579	$52.66	$52.65	$52.70
Purchase #7	$147.64	7.187%	$158.2509	$158.25	$158.25	$158.30
7 purchase totals =	$969.34		$1,034.5106	$1,034.52	$1,034.55	$1,034.60