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	$191.52	11.393%	$213.3399	$213.34	$213.35	$213.30
Purchase #2	$50.58	11.847%	$56.5722	$56.57	$56.55	$56.60
Purchase #3	$88.41	11.539%	$98.6116	$98.61	$98.60	$98.60
Purchase #4	$177.54	12.870%	$200.3894	$200.39	$200.40	$200.40
Purchase #5	$91.96	12.337%	$103.3051	$103.31	$103.30	$103.30
Purchase #6	$96.71	5.239%	$101.7766	$101.78	$101.80	$101.80
Purchase #7	$194.86	6.846%	$208.2001	$208.20	$208.20	$208.20
7 purchase totals =	$891.58		$982.1949	$982.20	$982.20	$982.20