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	$227.88	9.407%	$249.3167	$249.32	$249.30	$249.30
Purchase #2	$164.96	12.336%	$185.3095	$185.31	$185.30	$185.30
Purchase #3	$40.37	7.731%	$43.491	$43.49	$43.50	$43.50
Purchase #4	$235.71	6.191%	$250.3028	$250.30	$250.30	$250.30
Purchase #5	$33.43	11.448%	$37.2571	$37.26	$37.25	$37.30
Purchase #6	$12.98	5.493%	$13.693	$13.69	$13.70	$13.70
Purchase #7	$248.93	11.839%	$278.4008	$278.40	$278.40	$278.40
7 purchase totals =	$964.26		$1,057.7709	$1,057.77	$1,057.75	$1,057.80