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	$98.76	13.173%	$111.7697	$111.77	$111.75	$111.80
Purchase #2	$33.72	5.517%	$35.5803	$35.58	$35.60	$35.60
Purchase #3	$121.44	10.365%	$134.0273	$134.03	$134.05	$134.00
Purchase #4	$126.63	9.538%	$138.708	$138.71	$138.70	$138.70
Purchase #5	$157.52	4.318%	$164.3217	$164.32	$164.30	$164.30
Purchase #6	$67.31	5.590%	$71.0726	$71.07	$71.05	$71.10
Purchase #7	$221.69	12.367%	$249.1064	$249.11	$249.10	$249.10
7 purchase totals =	$827.07		$904.5860	$904.59	$904.55	$904.60