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	$163.25	10.243%	$179.9717	$179.97	$179.95	$180.00
Purchase #2	$39.75	8.178%	$43.0008	$43.00	$43.00	$43.00
Purchase #3	$125.64	13.336%	$142.3954	$142.40	$142.40	$142.40
Purchase #4	$185.41	13.279%	$210.0306	$210.03	$210.05	$210.00
Purchase #5	$185.83	7.310%	$199.4142	$199.41	$199.40	$199.40
Purchase #6	$79.27	4.337%	$82.7079	$82.71	$82.70	$82.70
Purchase #7	$171.72	13.189%	$194.3682	$194.37	$194.35	$194.40
7 purchase totals =	$950.87		$1,051.8888	$1,051.89	$1,051.85	$1,051.90