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	$182.97	7.165%	$196.0798	$196.08	$196.10	$196.10
Purchase #2	$156.87	10.342%	$173.0935	$173.09	$173.10	$173.10
Purchase #3	$196.74	13.664%	$223.6226	$223.62	$223.60	$223.60
Purchase #4	$75.39	12.829%	$85.0618	$85.06	$85.05	$85.10
Purchase #5	$28.51	13.452%	$32.3452	$32.35	$32.35	$32.30
Purchase #6	$80.58	11.638%	$89.9579	$89.96	$89.95	$90.00
Purchase #7	$45.59	11.439%	$50.805	$50.81	$50.80	$50.80
7 purchase totals =	$766.65		$850.9658	$850.97	$850.95	$851.00