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	$170.77	12.132%	$191.4878	$191.49	$191.50	$191.50
Purchase #2	$124.78	13.176%	$141.221	$141.22	$141.20	$141.20
Purchase #3	$103.66	5.294%	$109.1478	$109.15	$109.15	$109.10
Purchase #4	$191.45	3.573%	$198.2905	$198.29	$198.30	$198.30
Purchase #5	$234.59	12.480%	$263.8668	$263.87	$263.85	$263.90
Purchase #6	$205.49	5.844%	$217.4988	$217.50	$217.50	$217.50
Purchase #7	$50.40	4.237%	$52.5354	$52.54	$52.55	$52.50
7 purchase totals =	$1,081.14		$1,174.0481	$1,174.06	$1,174.05	$1,174.00