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	$198.78	5.399%	$209.5121	$209.51	$209.50	$209.50
Purchase #2	$75.58	3.645%	$78.3349	$78.33	$78.35	$78.30
Purchase #3	$43.99	8.184%	$47.5901	$47.59	$47.60	$47.60
Purchase #4	$175.67	13.201%	$198.8602	$198.86	$198.85	$198.90
Purchase #5	$78.35	4.643%	$81.9878	$81.99	$82.00	$82.00
Purchase #6	$97.28	3.405%	$100.5924	$100.59	$100.60	$100.60
Purchase #7	$73.70	6.873%	$78.7654	$78.77	$78.75	$78.80
7 purchase totals =	$743.35		$795.6429	$795.64	$795.65	$795.70