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	$140.70	9.422%	$153.9568	$153.96	$153.95	$154.00
Purchase #2	$94.65	7.321%	$101.5793	$101.58	$101.60	$101.60
Purchase #3	$189.94	4.409%	$198.3145	$198.31	$198.30	$198.30
Purchase #4	$81.31	8.811%	$88.4742	$88.47	$88.45	$88.50
Purchase #5	$102.54	8.298%	$111.0488	$111.05	$111.05	$111.00
Purchase #6	$246.69	10.563%	$272.7479	$272.75	$272.75	$272.70
Purchase #7	$84.98	6.305%	$90.338	$90.34	$90.35	$90.30
7 purchase totals =	$940.81		$1,016.4595	$1,016.46	$1,016.45	$1,016.40