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	$106.29	4.776%	$111.3664	$111.37	$111.35	$111.40
Purchase #2	$111.84	5.825%	$118.3547	$118.35	$118.35	$118.40
Purchase #3	$57.32	5.593%	$60.5259	$60.53	$60.55	$60.50
Purchase #4	$122.30	11.537%	$136.4098	$136.41	$136.40	$136.40
Purchase #5	$158.27	8.720%	$172.0711	$172.07	$172.05	$172.10
Purchase #6	$91.57	6.454%	$97.4799	$97.48	$97.50	$97.50
Purchase #7	$149.90	9.825%	$164.6277	$164.63	$164.65	$164.60
7 purchase totals =	$797.49		$860.8355	$860.84	$860.85	$860.90