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	$229.80	11.435%	$256.0776	$256.08	$256.10	$256.10
Purchase #2	$8.87	12.759%	$10.0017	$10.00	$10.00	$10.00
Purchase #3	$91.40	10.187%	$100.7109	$100.71	$100.70	$100.70
Purchase #4	$52.88	11.678%	$59.0553	$59.06	$59.05	$59.10
Purchase #5	$190.35	4.503%	$198.9215	$198.92	$198.90	$198.90
Purchase #6	$183.64	9.611%	$201.2896	$201.29	$201.30	$201.30
Purchase #7	$97.78	8.294%	$105.8899	$105.89	$105.90	$105.90
7 purchase totals =	$854.72		$931.9465	$931.95	$931.95	$932.00