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	$115.98	9.664%	$127.1883	$127.19	$127.20	$127.20
Purchase #2	$85.61	8.320%	$92.7328	$92.73	$92.75	$92.70
Purchase #3	$50.88	4.513%	$53.1762	$53.18	$53.20	$53.20
Purchase #4	$54.55	13.168%	$61.7331	$61.73	$61.75	$61.70
Purchase #5	$123.92	5.338%	$130.5348	$130.53	$130.55	$130.50
Purchase #6	$193.94	7.343%	$208.181	$208.18	$208.20	$208.20
Purchase #7	$90.60	8.470%	$98.2738	$98.27	$98.25	$98.30
7 purchase totals =	$715.48		$771.8200	$771.81	$771.90	$771.80