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	$160.83	13.839%	$183.0873	$183.09	$183.10	$183.10
Purchase #2	$40.89	7.314%	$43.8807	$43.88	$43.90	$43.90
Purchase #3	$242.41	3.610%	$251.161	$251.16	$251.15	$251.20
Purchase #4	$72.86	7.597%	$78.3952	$78.40	$78.40	$78.40
Purchase #5	$199.62	5.726%	$211.0502	$211.05	$211.05	$211.10
Purchase #6	$101.49	13.736%	$115.4307	$115.43	$115.45	$115.40
Purchase #7	$41.61	3.678%	$43.1404	$43.14	$43.15	$43.10
7 purchase totals =	$859.71		$926.1455	$926.15	$926.20	$926.20