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	$106.37	5.164%	$111.8629	$111.86	$111.85	$111.90
Purchase #2	$195.40	3.276%	$201.8013	$201.80	$201.80	$201.80
Purchase #3	$116.28	5.646%	$122.8452	$122.85	$122.85	$122.80
Purchase #4	$162.51	4.162%	$169.2737	$169.27	$169.25	$169.30
Purchase #5	$171.28	10.598%	$189.4323	$189.43	$189.45	$189.40
Purchase #6	$78.49	5.160%	$82.5401	$82.54	$82.55	$82.50
Purchase #7	$197.92	5.286%	$208.3821	$208.38	$208.40	$208.40
7 purchase totals =	$1,028.25		$1,086.1376	$1,086.13	$1,086.15	$1,086.10