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	$22.43	13.414%	$25.4388	$25.44	$25.45	$25.40
Purchase #2	$99.45	12.468%	$111.8494	$111.85	$111.85	$111.80
Purchase #3	$126.36	5.292%	$133.047	$133.05	$133.05	$133.00
Purchase #4	$114.35	12.376%	$128.502	$128.50	$128.50	$128.50
Purchase #5	$170.32	12.326%	$191.3136	$191.31	$191.30	$191.30
Purchase #6	$54.60	11.614%	$60.9412	$60.94	$60.95	$60.90
Purchase #7	$186.35	5.201%	$196.0421	$196.04	$196.05	$196.00
7 purchase totals =	$773.86		$847.1341	$847.13	$847.15	$846.90