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	$61.39	13.672%	$69.7832	$69.78	$69.80	$69.80
Purchase #2	$112.86	9.267%	$123.3187	$123.32	$123.30	$123.30
Purchase #3	$231.61	13.164%	$262.0991	$262.10	$262.10	$262.10
Purchase #4	$137.98	3.355%	$142.6092	$142.61	$142.60	$142.60
Purchase #5	$236.96	13.334%	$268.5562	$268.56	$268.55	$268.60
Purchase #6	$151.32	12.615%	$170.409	$170.41	$170.40	$170.40
Purchase #7	$172.93	13.730%	$196.6733	$196.67	$196.65	$196.70
7 purchase totals =	$1,105.05		$1,233.4487	$1,233.45	$1,233.40	$1,233.50