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	$57.93	5.824%	$61.3038	$61.30	$61.30	$61.30
Purchase #2	$8.67	8.263%	$9.3864	$9.39	$9.40	$9.40
Purchase #3	$72.57	8.554%	$78.7776	$78.78	$78.80	$78.80
Purchase #4	$236.60	13.335%	$268.1506	$268.15	$268.15	$268.20
Purchase #5	$167.60	4.105%	$174.48	$174.48	$174.50	$174.50
Purchase #6	$41.88	3.434%	$43.3182	$43.32	$43.30	$43.30
Purchase #7	$103.95	9.235%	$113.5498	$113.55	$113.55	$113.50
7 purchase totals =	$689.20		$748.9664	$748.97	$749.00	$749.00