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	$170.54	9.497%	$186.7362	$186.74	$186.75	$186.70
Purchase #2	$128.85	12.401%	$144.8287	$144.83	$144.85	$144.80
Purchase #3	$117.76	3.795%	$122.229	$122.23	$122.25	$122.20
Purchase #4	$29.71	6.379%	$31.6052	$31.61	$31.60	$31.60
Purchase #5	$104.54	6.157%	$110.9765	$110.98	$111.00	$111.00
Purchase #6	$235.52	11.831%	$263.3844	$263.38	$263.40	$263.40
Purchase #7	$191.90	4.132%	$199.8293	$199.83	$199.85	$199.80
7 purchase totals =	$978.82		$1,059.5893	$1,059.60	$1,059.70	$1,059.50