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	$237.34	3.404%	$245.4191	$245.42	$245.40	$245.40
Purchase #2	$211.71	6.591%	$225.6638	$225.66	$225.65	$225.70
Purchase #3	$132.65	5.192%	$139.5372	$139.54	$139.55	$139.50
Purchase #4	$194.52	3.187%	$200.7194	$200.72	$200.70	$200.70
Purchase #5	$54.59	12.833%	$61.5955	$61.60	$61.60	$61.60
Purchase #6	$142.69	4.741%	$149.4549	$149.45	$149.45	$149.50
Purchase #7	$166.51	13.186%	$188.466	$188.47	$188.45	$188.50
7 purchase totals =	$1,140.01		$1,210.8559	$1,210.86	$1,210.80	$1,210.90