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	$35.81	13.441%	$40.6232	$40.62	$40.60	$40.60
Purchase #2	$140.89	8.228%	$152.4824	$152.48	$152.50	$152.50
Purchase #3	$162.35	10.723%	$179.7588	$179.76	$179.75	$179.80
Purchase #4	$167.55	4.543%	$175.1618	$175.16	$175.15	$175.20
Purchase #5	$147.32	13.192%	$166.7545	$166.75	$166.75	$166.80
Purchase #6	$144.52	9.471%	$158.2075	$158.21	$158.20	$158.20
Purchase #7	$131.39	5.837%	$139.0592	$139.06	$139.05	$139.10
7 purchase totals =	$929.83		$1,012.0474	$1,012.04	$1,012.00	$1,012.20