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	$116.34	4.224%	$121.2542	$121.25	$121.25	$121.30
Purchase #2	$29.79	11.857%	$33.3222	$33.32	$33.30	$33.30
Purchase #3	$166.38	5.432%	$175.4178	$175.42	$175.40	$175.40
Purchase #4	$107.97	3.336%	$111.5719	$111.57	$111.55	$111.60
Purchase #5	$153.25	13.723%	$174.2805	$174.28	$174.30	$174.30
Purchase #6	$245.96	9.605%	$269.5845	$269.58	$269.60	$269.60
Purchase #7	$142.34	9.783%	$156.2651	$156.27	$156.25	$156.30
7 purchase totals =	$962.03		$1,041.6962	$1,041.69	$1,041.65	$1,041.80