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	$78.39	9.204%	$85.605	$85.61	$85.60	$85.60
Purchase #2	$223.28	9.204%	$243.8307	$243.83	$243.85	$243.80
Purchase #3	$94.61	5.830%	$100.1258	$100.13	$100.15	$100.10
Purchase #4	$160.60	13.345%	$182.0321	$182.03	$182.05	$182.00
Purchase #5	$130.41	9.597%	$142.9254	$142.93	$142.95	$142.90
Purchase #6	$138.44	9.268%	$151.2706	$151.27	$151.25	$151.30
Purchase #7	$202.28	3.132%	$208.6154	$208.62	$208.60	$208.60
7 purchase totals =	$1,028.01		$1,114.4050	$1,114.42	$1,114.45	$1,114.30