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	$93.27	5.688%	$98.5752	$98.58	$98.60	$98.60
Purchase #2	$97.58	6.522%	$103.9442	$103.94	$103.95	$103.90
Purchase #3	$71.77	7.477%	$77.1362	$77.14	$77.15	$77.10
Purchase #4	$127.63	4.108%	$132.873	$132.87	$132.85	$132.90
Purchase #5	$76.55	11.589%	$85.4214	$85.42	$85.40	$85.40
Purchase #6	$196.27	11.430%	$218.7037	$218.70	$218.70	$218.70
Purchase #7	$68.95	4.179%	$71.8314	$71.83	$71.85	$71.80
7 purchase totals =	$732.02		$788.4851	$788.48	$788.50	$788.40