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	$77.34	12.535%	$87.0346	$87.03	$87.05	$87.00
Purchase #2	$49.29	6.160%	$52.3263	$52.33	$52.35	$52.30
Purchase #3	$54.81	9.169%	$59.8355	$59.84	$59.85	$59.80
Purchase #4	$102.64	6.578%	$109.3917	$109.39	$109.40	$109.40
Purchase #5	$73.32	9.339%	$80.1674	$80.17	$80.15	$80.20
Purchase #6	$225.85	7.361%	$242.4748	$242.47	$242.45	$242.50
Purchase #7	$208.78	3.579%	$216.2522	$216.25	$216.25	$216.30
7 purchase totals =	$792.03		$847.4825	$847.48	$847.50	$847.50