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	$116.41	9.118%	$127.0243	$127.02	$127.00	$127.00
Purchase #2	$217.77	3.326%	$225.013	$225.01	$225.00	$225.00
Purchase #3	$76.28	6.519%	$81.2527	$81.25	$81.25	$81.30
Purchase #4	$198.30	5.373%	$208.9547	$208.95	$208.95	$209.00
Purchase #5	$81.44	11.160%	$90.5287	$90.53	$90.55	$90.50
Purchase #6	$226.26	4.686%	$236.8625	$236.86	$236.85	$236.90
Purchase #7	$70.62	11.105%	$78.4624	$78.46	$78.45	$78.50
7 purchase totals =	$987.08		$1,048.0983	$1,048.08	$1,048.05	$1,048.20