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	$239.40	9.223%	$261.4799	$261.48	$261.50	$261.50
Purchase #2	$26.33	6.596%	$28.0667	$28.07	$28.05	$28.10
Purchase #3	$54.82	4.529%	$57.3028	$57.30	$57.30	$57.30
Purchase #4	$178.40	12.183%	$200.1345	$200.13	$200.15	$200.10
Purchase #5	$126.79	3.746%	$131.5396	$131.54	$131.55	$131.50
Purchase #6	$214.59	12.105%	$240.5661	$240.57	$240.55	$240.60
Purchase #7	$14.88	3.288%	$15.3693	$15.37	$15.35	$15.40
7 purchase totals =	$855.21		$934.4589	$934.46	$934.45	$934.50