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	$109.60	8.242%	$118.6332	$118.63	$118.65	$118.60
Purchase #2	$83.50	13.575%	$94.8351	$94.84	$94.85	$94.80
Purchase #3	$153.72	9.571%	$168.4325	$168.43	$168.45	$168.40
Purchase #4	$78.33	9.372%	$85.6711	$85.67	$85.65	$85.70
Purchase #5	$100.43	8.867%	$109.3351	$109.34	$109.35	$109.30
Purchase #6	$147.60	13.437%	$167.433	$167.43	$167.45	$167.40
Purchase #7	$129.64	9.869%	$142.4342	$142.43	$142.45	$142.40
7 purchase totals =	$802.82		$886.7742	$886.77	$886.85	$886.60