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	$145.31	3.550%	$150.4685	$150.47	$150.45	$150.50
Purchase #2	$105.78	8.559%	$114.8337	$114.83	$114.85	$114.80
Purchase #3	$128.80	3.640%	$133.4883	$133.49	$133.50	$133.50
Purchase #4	$118.72	12.292%	$133.3131	$133.31	$133.30	$133.30
Purchase #5	$93.87	3.591%	$97.2409	$97.24	$97.25	$97.20
Purchase #6	$250.59	11.195%	$278.6436	$278.64	$278.65	$278.60
Purchase #7	$37.61	13.174%	$42.5647	$42.56	$42.55	$42.60
7 purchase totals =	$880.68		$950.5528	$950.54	$950.55	$950.50