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	$198.72	11.668%	$221.9066	$221.91	$221.90	$221.90
Purchase #2	$242.63	5.149%	$255.123	$255.12	$255.10	$255.10
Purchase #3	$38.25	5.494%	$40.3515	$40.35	$40.35	$40.40
Purchase #4	$142.26	5.722%	$150.4001	$150.40	$150.40	$150.40
Purchase #5	$127.52	8.267%	$138.0621	$138.06	$138.05	$138.10
Purchase #6	$43.83	10.421%	$48.3975	$48.40	$48.40	$48.40
Purchase #7	$125.50	6.404%	$133.537	$133.54	$133.55	$133.50
7 purchase totals =	$918.71		$987.7778	$987.78	$987.75	$987.80