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	$105.75	5.308%	$111.3632	$111.36	$111.35	$111.40
Purchase #2	$226.86	8.332%	$245.762	$245.76	$245.75	$245.80
Purchase #3	$104.37	12.722%	$117.648	$117.65	$117.65	$117.60
Purchase #4	$131.88	3.543%	$136.5525	$136.55	$136.55	$136.60
Purchase #5	$23.91	11.207%	$26.5896	$26.59	$26.60	$26.60
Purchase #6	$92.75	7.829%	$100.0114	$100.01	$100.00	$100.00
Purchase #7	$245.76	13.402%	$278.6968	$278.70	$278.70	$278.70
7 purchase totals =	$931.28		$1,016.6235	$1,016.62	$1,016.60	$1,016.70