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	$5.49	4.208%	$5.721	$5.72	$5.70	$5.70
Purchase #2	$92.70	7.677%	$99.8166	$99.82	$99.80	$99.80
Purchase #3	$68.53	7.744%	$73.837	$73.84	$73.85	$73.80
Purchase #4	$54.60	9.665%	$59.8771	$59.88	$59.90	$59.90
Purchase #5	$249.50	11.273%	$277.6261	$277.63	$277.65	$277.60
Purchase #6	$216.39	11.596%	$241.4826	$241.48	$241.50	$241.50
Purchase #7	$231.52	11.337%	$257.7674	$257.77	$257.75	$257.80
7 purchase totals =	$918.73		$1,016.1278	$1,016.14	$1,016.15	$1,016.10