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	$191.63	12.324%	$215.2465	$215.25	$215.25	$215.20
Purchase #2	$138.64	11.834%	$155.0467	$155.05	$155.05	$155.00
Purchase #3	$113.59	11.818%	$127.0141	$127.01	$127.00	$127.00
Purchase #4	$69.78	10.228%	$76.9171	$76.92	$76.90	$76.90
Purchase #5	$141.86	6.654%	$151.2994	$151.30	$151.30	$151.30
Purchase #6	$43.69	12.348%	$49.0848	$49.08	$49.10	$49.10
Purchase #7	$118.57	10.572%	$131.1052	$131.11	$131.10	$131.10
7 purchase totals =	$817.76		$905.7138	$905.72	$905.70	$905.60