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	$234.69	7.271%	$251.7543	$251.75	$251.75	$251.80
Purchase #2	$108.36	3.287%	$111.9218	$111.92	$111.90	$111.90
Purchase #3	$44.79	12.581%	$50.425	$50.43	$50.45	$50.40
Purchase #4	$97.26	7.147%	$104.2112	$104.21	$104.20	$104.20
Purchase #5	$50.86	3.363%	$52.5704	$52.57	$52.55	$52.60
Purchase #6	$112.78	12.817%	$127.235	$127.24	$127.25	$127.20
Purchase #7	$138.82	8.753%	$150.9709	$150.97	$150.95	$151.00
7 purchase totals =	$787.56		$849.0886	$849.09	$849.05	$849.10