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	$66.60	7.562%	$71.6363	$71.64	$71.65	$71.60
Purchase #2	$172.65	13.596%	$196.1235	$196.12	$196.10	$196.10
Purchase #3	$79.64	3.390%	$82.3398	$82.34	$82.35	$82.30
Purchase #4	$82.80	5.501%	$87.3548	$87.35	$87.35	$87.40
Purchase #5	$186.39	9.371%	$203.8566	$203.86	$203.85	$203.90
Purchase #6	$244.60	11.478%	$272.6752	$272.68	$272.70	$272.70
Purchase #7	$79.68	13.439%	$90.3882	$90.39	$90.40	$90.40
7 purchase totals =	$912.36		$1,004.3744	$1,004.38	$1,004.40	$1,004.40