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	$181.41	13.149%	$205.2636	$205.26	$205.25	$205.30
Purchase #2	$144.61	10.624%	$159.9734	$159.97	$159.95	$160.00
Purchase #3	$142.63	6.533%	$151.948	$151.95	$151.95	$151.90
Purchase #4	$235.82	11.276%	$262.4111	$262.41	$262.40	$262.40
Purchase #5	$65.57	10.224%	$72.2739	$72.27	$72.25	$72.30
Purchase #6	$204.72	7.254%	$219.5704	$219.57	$219.55	$219.60
Purchase #7	$39.85	8.410%	$43.2014	$43.20	$43.20	$43.20
7 purchase totals =	$1,014.61		$1,114.6418	$1,114.63	$1,114.55	$1,114.70